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Solid-state transformations are important in many areas of science and technology. Herein, a model for predicting the relative energies of stationary points along the reaction pathways for stress-induced solid-state transformations is assessed and applied. The model is based on a second-order expansion of the energy of the system with respect to changes in the unit cell, and requires a small number of parameters that can be obtained through quantum chemical calculations. Comparison of the model with the results of quantum chemical calculations indicates that the model accurately reproduces changes in energy occurring during stress-induced transformations over a reasonable range of stresses. A procedure for applying the model to identify stress tensors that are most likely to promote a desired reaction is illustrated. The results also indicate that this procedure provides insight into the connection between the form of a stress tensor and the changes in energy occurring during a stress-induced solid-state transformation. Key words: mechanochemistry, models, density functional theory, materials, solid state, 1. Introduction Chemical transformations occur in conjunction with changes in energy. For instance, the kinetics of a reaction are influenced by the energy barrier separating the reactants from the products [...]

Recent experimental studies of a spiro-linked anthracenone (A)-naphthalene (N) compound (AN) in hutyronitrile (BuCN) solution (Dohkowski et al., J. Phys. Chem. A 2019, 123, 6978) proposed an excited-state energy dissipation pathway [[.sup.1]nn* (N) + [.sup.1][pi][pi]* (A)][??][.sup.1]n[pi]* (A)[??][.sup.3]n[pi]* (A)[.sup.1][pi][pi]* (N). However, a detailed theoretical study employing comhined density functional theory and multireference configuration interaction methods, performed in the present work, suggests that the photoexcitation decay follows a different pathway. In BuCN solution, the intersystem crossing (ISC) follows the well-established El-Sayed rule and involves the [.sup.1][pi][pi]* (A) state which is found to be the lowest excited triplet state localized on the anthracenone moiety. Because the Dexter triplet excitation energy transfer (TEET) to the first excited triplet state of the naphthalene subunit is forbidden in [C.sub.2v] symmetry, it is mandatory to go beyond the Condon approximation in modeling this process. Nonadiabatic coupling matrix elements were computed to obtain a TEET rate different from zero. Our calculations yield time constants of 5 ps for the [.sup.1]n[pi]* (A)[??][.sup.3][pi][pi]* (A) ISC and of 3 ps for the subsequent [.sup.3][pi][pi]* (A)[??][.sup.3][pi][pi]* (N) TEET in BuCN whereas the energy dissipation involving the [.sup.3]n[pi]* (A) state as an intermediate occurs on a much longer time scale. Key words: multireference methods, intersystem crossing, nonadiabatic coupling, intramolecular triplet energy transfer, solvent effects, 1. Introduction Excitation energy transfer (EET) between a triplet sensitizer and a triplet acceptor is a common chemical process used to photoinitiate radical reactions (1) or triplet-triplet annihilation upconversion. (2) [...]

The structural, elastic, electronic, and magnetic properties of the CrCoSi, MnCoSi parent half-Heusler (HH) alloys, and their CrMn[Co.sub.2][Si.sub.2] derivative double half-Heusler (DHH) compound are studied, utilizing the augmented plane wave method, which is based on density functional theory and implemented in the WIEN2k code. The stability of HH structure of the CrCoSi and MnCoSi alloys has been checked for their non-magnetic and ferromagnetic phases, leading to that the latter phase of the type I arrangement is the most stable. The CrMn[Co.sub.2][Si.sub.2] DHH alloy, derivative from the found structural and magnetic ground states of CrCoSi and MnCoSi HH alloys, is constructed and investigated. This DDH as well as its CrCoSi parent HH are found to be resistant to deformation and can be classified as ductile materials, whereas the MnCoSi compound is brittle. By the gradient generalized approximation (GGA), the electronic structures of CrCoSi, MnCoSi, and CrMn[Co.sub.2][Si.sub.2]compounds exhibit a metallic behavior in the spin-up channel and a semiconducting behavior in the spin-dn channel, with band gaps (half-metallic gaps) of 0. 851(0.020), 0.852(0.021), and 0.531(0.002) eV, respectively. The half-metallicity of CrMn[Co.sub.2][Si.sub.2] DHH is retained with smaller (larger) band gap (half-metallic gap) of 0.38(0.106) eV than that of GGA, using GGA + U approximation. In addition, the total magnetic moments are found to be 1, 2, and 3 [[mu].sub.B] for CrCoSi, MnCoSi, and CrMn[Co.sub.2][Si.sub.2], respectively. Therefore, these alloys can be good candidates for spinitronic applications due to their half-metallicity. Key words: half-metal, heusler alloys, spin polarization, mechanical stability, FP-LAPW, 1. Introduction Spin-based electronics has grown into a significant field of study that spans a wide range of high spin-polarized materials, used in spintronic devices. It overcomes the limitations of [...]

Integrating chemical dopants into a pure lattice has fueled a novel concept of tuning the physical and chemical properties of existing materials under and beyond ambient conditions. By using density functional theory (DFT) calculations, we report the structural, electronic, elastic, and optical properties of pure and Mg-doped LaAl[O.sub.3] structure ([La.sub.1- x][Mg.sub.x]Al[O.sub.3] and La[Al.sub.1-x][Mg.sub.x][O.sub.3]), respectively, with the doping concentrations of x = 0%, 20%, 40%, 60%, 80%, and 100%. Our results show that the doping of Mg along La sites introduce new band (s, p) in the valence bands that is moved towards the conduction bands with increase of doping ration (at x = 60% with a reduced bandgap of 0.04 eV), as well as indirect to direct bandgap transition along Al sites. The density of states shows that the valence band shifts towards the Fermi level by inducing a metallicity in [La.sub.1- x][Mg.sub.x]Al[O.sub.3] format at 60% configuration. Elastically, LaAl[O.sub.3] experiences brittle to ductile transition for both doping systems except La[Al.sub.1-x][Mg.sub.x][O.sub.3] at 40% configuration. The higher ranges of optical peaks for both systems are identified for 0%-40% ranges as compared to other configurations. Fortunately, this study reveals the tunability of LaAl[O.sub.3] structure in structural, electronic, elastic, and optical aspects, and also extends the availability of this material for future optoelectronic and mechanical applications. Key words: doping, band gap, density of states, valence band, Fermi level, 1. Introduction The accelerating depletion of sustainable energy sources caused by the rapid consumption of fossil fuels has alarmed modern societies to explore highly efficient, versatile, and eco-friendly energy sources [...]

Solvent as a complex environment can surround solute molecules and modify their function. In this work, different solutesolvent interaction effects on the nonlinear optical behavior of some azo dyes were studied at the molecular level. In this case, spectroscopic technique and density functional theory were used. According to the results, molecular dipole transition, changes between ground and excited state dipole moments, substituent, and environment polarity play considerable effects on the molecular nonlinear optical responses. In addition to solvent effects on the molecular first- and second-order hyperpolarizability, the two-photon absorption cross-section is also modified due to solvent-induced interactions. Moreover, the determination of the contribution of dominant solvent effects on the molecular nonlinear optical behavior can facilitate the studies on the application of optical samples in designing various optical systems. Key words: hyperpolarizability, density functional theory, spectroscopy, two-photon cross-section, 1. Introduction Optical materials with nonlinear characteristics play significant roles in optics and photonics. By exploiting basic science, researchers are active in various laboratories to synthesize materials with unique nonlinear [...]

In this paper, we examined the effects of transition metal replacement and ordering in 2D [M.sub.3][C.sub.2][O.sub.2] MXene on the electronic structure and thermal and electrical conductivities using the density functional theory and also Boltzmann's transport theory within the constant relaxation time approximation. We derived the following oxygen-functionalized ordered double-metal MXenes T[i.sub.2]Y[C.sub.2][O.sub.2], [Y.sub.2]Ti[C.sub.2][O.sub.2], S[c.sub.2]Y[C.sub.2][O.sub.2], and [Y.sub.2]Sc[C.sub.2][O.sub.2] through the surface and sub-layer tuning. The results revealed that the ordered MXenes give rise to different electronic structure and transport properties. The electronic thermal conductivities obtained in terms of the relaxation time increase with increase in absolute temperature, while the electrical conductivities decrease with increase in temperature. The respective transport properties of [Y.sub.2]Ti[C.sub.2][O.sub.2] and S[c.sub.2]Y[C.sub.2][O.sub.2] were found to be enhanced due to the increased squared band velocity, density of state, and low Seebeck coefficient compared to T[i.sub.2]Y[C.sub.2][O.sub.2] and [Y.sub.2]Sc[C.sub.2][O.sub.2] MXenes. Generally, the MXene materials investigated in this work were found to possess metallic properties with the existence of energy overlap around the Fermi level. The computed formation energies support chemical stability in all the materials. Key words: MXenes, density functional theory, Boltzmann's theory, thermal conductivity, electrical conductivity, Introduction Two-dimensional (2D) materials have emerged as the cornerstone of device fabrications due to their wide surface area compared to their bulk counterparts. Also, in contrast to bulk materials, 2D [...]

Half-metallic ferromagnetism is reported in RbTi[O.sub.3] and CsTi[O.sub.3] compounds under the exchange-correlation functions GGA, TB-mBJ, and GGA + U using the full-potential linearized augmented plane wave method. Spin-resolved calculations were carried out and implemented within the framework of density functional theory. The compounds exhibit energy band gap in the spin-up direction using three functionals of PBE-GGA, TB-mBJ, and GGA + U. A larger band gap is predicted to occur in both the compounds with the use of TB-mBJ potential. A higher value of magnetic moment is evidenced for RbTi[O.sub.3] and CsTi[O.sub.3] using the PBE-GGA method as compared to the mBJ and GGA + U methods. The Curie temperature was determined for the compounds at equilibrium and reduced volumes. It is reported that the Curie temperature increases with the increase in hydrostatic pressure. With the help of second-order elastic constants, the Debye temperature and anisotropy factor were predicted for the compounds. Key words: PBE-GGA, TB-mBJ, GGA + U methods, half-metallic ferromagnetism, Curie and Debye temperatures, 1. Introduction Half-metallic ferromagnetic materials have become the focus of materials research today due to their increased efficiency in data storage, retrieval, and distribution. These half-metallic materials are the new [...]

The photophysical properties of four 1,3,6-trisubstituted pyrazolo[3,4-d][1,2,3]triazoles were studied by a combination of UV--vis and fluorescence spectroscopy as well as density functional theory (DFT) and time-dependent DFT calculations. All four compounds are weakly fluorescent. Upon protonation with trifluoroacetic acid, all compounds display a drastic luminescence turn-on. The addition of excess trifluoroacetic acid further enhances the luminescence intensity, which is tentatively attributed to the formation of extended hydrogen bonding network rather than the formation of doubly protonated 1,3,6-trisubstituted pyrazolo[3,4-d][1,2,3]triazoles. All new compounds were characterized by nuclear magnetic resonance and X-ray crystallography. Key words: luminescence, UV--vis spectroscopy, pyrazole, triazole, fused N-heterocycles, Introduction Nitrogen-rich fused heterocycles are an important class of compounds with wide applications in the rapidly expanding fields of medicinal chemistry, drug discovery, and functional material development. (1-8) Pyrazolo[3,4-d][1,2,3]triazoles are [...]

With our continuing interest in the chemistry of cationic horanes, we have synthesized the tetrafluoroborate salt of 1-dimesitylboron-4-(N-methyl-9-acridinium)-phenylene, which acts as a turn-on fluoride anion sensor, visibly changing from yellow to orange upon binding fluoride. To understand this reactivity, we spectroscopically and computationally analyzed the cation and fluoroborate adduct. Ultraviolet-visible spectroscopy and time-dependent density functional theory calculations revealed the basis of the color change to be a low energy redshift in a intramolecular charge transfer band. Electrochemical studies were undertaken to further probe this system. Cyclic voltammetry indicated a reversible one-electron reduction for the cation and a cathodic shift of -0.12 V in the first reduction wave upon fluoride binding. Chemical reduction of the cation yielded the acridine borane radical, which was verified by electron paramagnetic resonance spectroscopy. Key words: boron, carbenium, fluoride ion sensing, acridine radical Notre intérêt constant pour la chimie des boranes cationiques nous a amenés à synthétiser le sel tétrafluoroborate du 1-dimésitylbore-4-(N-méthyl-9-acridinium)-phénylène, qui agit comme détecteur d'anions fluorure activable en changeant visiblement de couleur, passant du jaune à l'orange, lorsqu'il se lie au fluorure. Pour comprendre cette réactivité, nous avons analysé par des méthodes spectroscopiques et computationnelles le cation et l'adduit fluoroborate. La spectroscopic UV-visible et des calculs basés sur la théorie de la fonctionnelle de la densité dépendante du temps (TD-DFT) ont révélé que le changement de couleur était attribuable à un déplacement vers le rouge d'une bande d'absorption de faible énergie qui découle d'un transfert de charge intramoléculaire. Nous avons entrepris des expériences électrochimiques pour étudier davantage ce système. La voltampérométrie cyclique a permis d'établir que le cation subissait une réduction réversible à un électron et a révélér un déplacement cathodique de -0,12 V dans la première onde de réduction lorsque le fluorure se lie au bore. La réduction chimique du cation a donné lieu au radical acridine borane, dont l'identité a été vérifiée par spectroscopic de résonance paramagnétique électronique (RPE). [Traduit par la Rédaction] Mots-clés : bore, carbénium, détection d'ions fluorure, radical acridine, 1. Introduction Fluoride anion recognition has become an attractive research area in recent decades due to concerns regarding this anion's potential toxicity to humans and the environment. (1-3) One conventional [...]

Adenyl urea derivative 1, which exhibits anion interaction, has been synthesized and characterized. With reference to the earlier reported compounds 2 and 3, compound 1 shows interaction to basic anions [F.sup.-] and pyruvate in [CHCl.sub.3]. The binding interaction has been illustrated by fluorescence, UV-vis, and [.sup.1]H NMR spectroscopic methods. The conformational behavior and the binding features of 1 with [F.sup.-] and pyruvate in [CHCl.sub.3] are explained by theoretical study. Key words: molecular recognition, adenyl urea, fluoride binding, pyruvate binding, DFT calculation Nous avons synthetise et caracterise le derive d'adenyluree 1 dote de la propriete d'interaction avec des anions. En se reportant aux composes 2 et 3 publies anterieurement, nous avons observe que le compose 1 interagit avec les anions basiques [F.sup.-] et le pyruvate dans le [CHCl.sub.3]. Nous avons represents cette interaction liante par des methodes spectroscopiques (fluorescence, UV visible et RMN [.sup.1]H). Nous expliquons par une etude theorique le comportement conformationnel et les caracteristiques de liaison du compose 1 avec les anions [F.sup.-] et le pyruvate dans le [CHCl.sub.3]. [Traduit par la Redaction.] Mots-cles : reconnaissance moleculaire, adenyluree, liaison au fluorure, liaison au pyruvate, calculs DFT, 1. Introduction Design and synthesis of molecular scaffold based on nucleobase is of considerable interest in the area of molecular recognition. (1) Among the different nucleobases, adenine draws attention due [...]

Increasing demands on producing environmentally friendly products are becoming a driving force for designing highly active catalysts. Thus, surfaces that efficiently catalyse the nitrogen reduction reactions are greatly sought in moderating air-pollutant emissions. This contribution aims to computationally investigate the hydrodenitrogenation (HDN) networks of pyridine over the [gamma]-M[o.sub.2]N(111) surface using a density functional theory (DFT) approach. Various adsorption configurations have been considered for the molecularly adsorbed pyridine. Findings indicate that pyridine can be adsorbed via side-on and end-on modes in six geometries in which one adsorption site is revealed to have the lowest adsorption energy (-45.3 kcal/mol). Over a nitrogen hollow site adsorption site, initial HDN steps proceed by the stepwise hydrogenation of pyridine into piperidine followed by the Langmuir--Hinshelwood mechanism. The obtained findings are the first to theoretically model the hydrogenation pathways of pyridine to form piperidine and then the hydrogenolysis of piperidine producing [C.sub.5][H.sub.12] and N[H.sub.3] over metal nitride. These paved the way for further investigations to better understanding such an important nitrogen removal reactions. Key words: hydrotreating processes, heterogeneous catalysts, molybdenum nitride [gamma]-M[o.sub.2]N, heteroatoms, aromatic rings, pyridine, density functional theory. La demande croissante pour la fabrication de produits écologiques est en voie de devenir une force motrice pour la conception de catalyseurs hautement actifs. On recherche donc dans plusieurs milieux des surfaces qui cataly-sent efficacement les réactions de réduction de l'azote afin de limiter les émissions de polluants atmosphériques. Dans le cadre des présents travaux, nous avons voulu étudier par calculs théoriques les réseaux d'hydrodénitrogénation (HDN) de la pyridine sur une surface de [gamma]-M[o.sub.2]N(111) à l'aide de la théorie de la fonctionnelle de la densité (DFT). Nous avons considéré la molécule de pyridine adsorbée selon diverses configurations d'adsorption. Les résultats indiquent que la pyridine peut être adsorbée selon les modes à plat et à la verticale, déclinés en six configurations géométriques parmi lesquelles nous avons identifié un site d'adsorption dont l'énergie d'adsorption était la plus faible (-45,3 kcal/mol. Sur le site d'adsorption formé par un creux dans les atomes d'azote, les premières étapes de l'HDN consistent en une série d'hydrogénations séquentielles de la pyridine en pipéridine suivant le mécanisme de Langmuir--Hinshelwood. Ces travaux sont les premiers à modéliser théoriquement les mécanismes d'hydrogénation de la pyridine en pipéridine, puis d'hydrogénolyse de la pipéridine pour produire du pentane ([C.sub.5][H.sub.12]) et de l'ammoniac (N[H.sub.3]) sur un nitrure métallique. Ils ouvrent ainsi la voie à d'autres recherches en vue de mieux comprendre des réactions aussi importantes dans l'élimination de composés azotés. [Traduit par la Rédaction] Mots-clés : procédés d'hydrotraitement, catalyseurs hétérogènes, nitrure de molybdène [gamma]-M[o.sub.2]N, hétéroatomes, noyaux aromatiques, pyridine, théorie de la fonctionnelle de la densité., 1. Introduction From the high level of hydrotreating processes used worldwide, it is highly desired to reduce the emissions of S[O.sub.x] and N[O.sub.x] through the combustion of oil fragments in [...]

The band gaps of three forms of polyaniline (PANI) are calculated using the DFT method with the B3LYP functional and SV(P) basis set. This marks the first time that the band gap for this polymer has been calculated using this DFT method. The calculations include an investigation of the effect of varying the benzoid--quinoid structural units, the effect of increasing oligomer length, and the inclusion of Michael's addition structures, which could be residual in the polymer depending on the chosen synthetic method. All results were compared with the experimentally determined band gap of 1.5 eV as typically reported in the literature. A commonly used structural motif of alternating benzoid-quinoid units and a ratio of 0.5:0.5 benzoid--quinoid resulted in a computed band gap of 1.9 eV. Inclusion of one extra quinoid unit gave rise to a band gap of 1.3 eV. Incorporation of a Michael's addition structure was found to dominate the band gap calculation, yielding a localized LUMO and a band gap of 1.3 eV that was insensitive to the polymer chain length and composition. Key words: polyaniline, B3LYP/def SV(P), band gap, computational chemistry, TurboMol. Nous avons calculé les bandes interdites de trois formes de polyaniline (PANI) à l'aide de la méthode DFT avec la fonctionnelle B3LYP et la base SV(P). Les calculs de la bande interdite avec cette méthode DFT constituent une première pour ce polymère. Ces calculs permettent d'étudier les effets de la variation des unités structurales benzoïdes et quinoïdes et de l'augmentation de la longueur des oligomères, ainsi que l'inclusion des structures d'addition de Michael qui pourraient être présentes à titre résiduel dans le polymère selon la méthode synthétique choisie. Tous les résultats ont été comparés à la bande interdite déterminée expérimentalement de 1,5 eV, qui correspond à la valeur généralement rapportée dans la littérature. Le résultat du calcul de la bande interdite effectué avec un motif structural communément utilisé, qui consiste à alterner les unités benzoïdes et quinoïdes, et un rapport benzoïde-quinoïde de 0,5 : 0,5 était de 1,9 eV. Cette valeur s'est établi à 1,3 eV avec l'inclusion d'une unité quinoïde supplémentaire. Nous avons constaté que l'effet de l'incorporation d'une structure d'addition de Michael était majeur dans le calcul de la bande interdite, donnant lieu à une LUMO localisée et à une bande interdite de 1,3 eV indépendante de la longueur et de la composition de la chaîne de polymère. [Traduit par la Rédaction] Mots-clés : polyaniline, B3LYP/def SV(P), bande interdite, chimie computationnelle, TurboMol., 1. Introduction Polyaniline (PANI) is an intrinsically conductive organic polymer. It is one of the more robust organic conductive polymers, as it is air stable and convenient to synthesize. PANI [...]

Thymine-1-acetic acid (TAA) is a modified nucleobase often used to add thymine functionality to materials. This study reports the Raman band assignments for TAA by comparing its experimental and density functional theory (DFT) simulated Raman spectra. Further comparison of experimental surface-enhanced Raman spectroscopy (SERS) of TAA on silver nanoparticles (Ag NPs) with simulated spectra of various complexes of x[Ag.sup.+] (x = 1, 2, or 3) and TAA reveals its likely adsorption orientation on the Ag NPs. This is one of the few studies that has achieved reasonably accurate simulation of SERS by employing multiple unconnected [Ag.sup.+] ions, which could represent a compromise between a single atom or ion on one hand and a computationally expensive cluster on the other. Key words: SERS, DFT, thymine-1-acetic acid, adsorption orientation, modified nucleobase. L'acide thymine-1-acetique (ATA) est une nucleobase modifiee souvent employee pour ajouter une fonctionnalite thymine a des materiaux. Dans cette etude, nous avons etabli l'assignation des bandes Raman du spectre de l'ATA en comparant le spectre Raman experimental a celui calcule selon la theorie de la fonctionnelle de la densite (DFT). Une comparaison plus poussee des spectres de diffusion Raman exaltee de surface (DRES) experimentaux de l'ATA adsorbe sur des nanoparticules d'argent (NP d'Ag) a des spectres theoriques de divers complexes de x[Ag.sup.+] (x = 1, 2 ou 3) avec l'ATA revele l'orientation probable de l'adsorption de cette molecule sur les NP d'Ag. Il s'agit de l'une des rares etudes a avoir realise une simulation raisonnablement precise du spectre DRES en utilisant plusieurs ions d'[Ag.sup.+] non connectes, ce qui pourrait constituer un compromis entre un atome ou un ion unique d'une part, et un agregat demandant de grandes ressources de calcul de l'autre. [Traduit par la Redaction] Mots-cles : DRES, DFT, acide thymine-1-acetique, orientation de l'adsorption, nucleobase modifiee., Introduction Surface-enhanced Raman spectroscopy (SERS) is widely known for its ability to boost the Raman signal of an analyte molecule adsorbed on gold or silver nanoparticles (NPs). (1) Comparing the [...]

In this paper, we have theoretically determined the possibility of adsorption of the gaseous C[H.sub.2][N.sub.2] molecule on the surface of [X.sub.12][Y.sub.12] nanocages, where X = B, Al, Ga and Y = N, P, As. The electronic structure calculations have been performed by density functional theory (DFT) using four functionals (i.e., B3LYP-D3, M06-2X, [omega]B97XD, and CAM-B3LYP), together with the 6-311G(d) basis function. We find that the adsorption of C[H.sub.2][N.sub.2] on top of the X-Y bond of the nanocage is the most preferred site for adsorption. The adsorption process is accompanied by a charge-transfer phenomenon, which results in a strong bond between the terminal N atom of diazomethane and the X atom of the nanocage. This gives rise to significant changes in the highest and lowest occupied molecular orbital (HOMO and LUMO, respectively) energies and thus attribute properties to the nanocages that enable them to act as building blocks of C[H.sub.2][N.sub.2] sensing materials. Key words: diazomethane, nanocage, DFT, NBO, QTAIM. Dans le cadre des présents travaux, nous avons réalisé une étude théorique pour déterminer la possibilité d'adsorption de la molécule de diazométhane (C[H.sub.2][N.sub.2]) gazeux à la surface de nanocages de formule [X.sub.12][Y.sub.12], où X = B, Al, Ga et Y = N, P, As. Nous avons modélisé la structure électronique selon des calculs de la théorie de la fonctionnelle de la densité (DFT), dans lesquels nous avons utilisé quatre fonctionnelles (soit B3LYPD3, M062X, xB97XD et CAMB3LYP) ainsi que la base 6311G(d). Nos résultats montrent que la liaison X-Y de la nanocage est le site d'adsorption privilégié du C[H.sub.2][N.sub.2]. Le processus d'adsorption est accompagné d'un phénomène de transfert de charge, qui se traduit par une forte liaison entre l'atome d'azote terminal du diazométhane et l'atome X de la nanocage. Ce phénomène donne lieu à des changements importants dans les énergies des orbitales moléculaires frontières (HOMO et LUMO) et confère donc aux nanocages des propriétés qui en font d'éventuels constituants de base pour former des matériaux de détection du C[H.sub.2][N.sub.2]. [Traduit par la Rédaction] Mots-clés : diazomethane, nanocage, théorie de la fonctionnelle de la densité, orbitales naturelles de liaison, théorie quantique des atomes dans les molecules., 1. Introduction Diazomethane (C[H.sub.2][N.sub.2])--ahighly toxic, flammable, and corrosive gas in its pure form at room temperature--can have a number of severe effects upon human health. (1) For example, inhalation of [...]

Abstract: Vibrational and spectral characterizations of 2-(6-oxo-2-thioxo tetrahydro pyrimidin-4(lh)-ylidene) hydrazine carboxamide (OTHHPYHC) were experimentally presented for the ground state using FTIR and FT-Raman and theoretically presented by density functional theory [...]

Abstract: Through a combined computational and isotopic labeling study, it has been observed that the activation energy for the aryl--alkyne ring closure of the azaborine containing 4-ethynyl-4a-aza-4b-boraphenanthrene is dramatically lower, [...]

Abstract: The crystal structure of 4-Methyl-N-(1-phenylethyl)-N'-(1-phenylethylidene) benzene sulfonohydrazide is disclosed, which is obtained from direct reaction between acetophenone tosylhydrazone and potassium tert-butoxide. Reaction mechanisms and the corresponding energy barriers were [...]

Abstract: We obtained accurate thermochemical properties for the ortho-, meta-, and para-dicarborane isomers ([C.sub.2][B.sub.10][H.sub.12]) by means of explicitly correlated high-level thermochemical procedures. The thermochemical properties include heats of formation, isomerization [...]

Abstract: Molybdenum is the only 4d metal found in almost all life. One such molybdenum-containing enzyme is sulfite oxidase, which also contains the dithiolene-molybdopterin ligand. Sulfite oxidase is essential in [...]

Abstract: Accurate MOF-FF parameter sets were determined for the ferrous and ferric forms of an iron-based metal--organic framework (MOF) called Fe-MOF-74. For this purpose, density functional theory (DFT) calculations were [...]

Abstract: The mechanism of the iridium-catalyzed functionalization of a primary C-H bond at the γ position of an alcohol (5) is investigated by density functional theory (DFT) calculations. A new [...]

Abstract: In this work, semi-experimental (SE) and theoretical equilibrium geometries of 10 sulfur-containing organic molecules, as well as 4 oxygenated ones, are determined by means of a computational protocol based [...]

Abstract: Density functional theory calculations were employed to study the catalytic mechanism, modes of activation, and origin of enantioselectivity of guanidine-catalyzed asymmetric Strecker reaction of N-benzhydryl imine with hydrogen cyanide. [...]

Abstract: Beryllium subphthalocyanines have been recently shown to be suitable candidates for photochemical devices if combined with appropriate donor systems. The ability of beryllium subphthalocyanines to self-assemble is explored for [...]

Abstract: We generalize the recently proposed steady-state density functional theory (SS-DFT) to spin-dependent cases and theoretically investigate the electronic and transport properties of a Mn-phthalocyanine molecule sandwiched between two graphene [...]

Abstract: Molecular structure and vibrational spectra of acetone, acetone-[d.sub.3], and acetone-[d.sub.6] were investigated by means of ab initio and density functional theory (DFT) calculations. The harmonic and anharmonic vibrational frequencies [...]

Abstract: A design strategy that including N atoms, N-oxides, and nitro groups into a cage azaadamantane at the same time was used to design 10 polyazaoxyadamantanes (PAOAs) and eight polynitroazaoxyadamantanes [...]

We have used density functional theory to investigate the electronic properties of two-dimensional porous sheets. The porous C and BN sheets based on graphene and α-graphyne are studied. It is found that the porous graphene is an insulator while porous α-graphyne has semiconducting properties. By substitution of C atoms by B and N atoms, the band gap becomes larger. The porous graphene-like and porous graphyne-like BN sheets show insulating behaviors. The nonzero band gap of these porous C and BN sheets may provide an opportunity to use them in nanoelectronic devices. Key words: porous graphene, porous graphyne, bn sheet, electronic property, density functional theory. Nous utilisons la theorie de la fonctionnelle de densite pour etudier les proprietes electroniques de couches bidimensionnelles poreuses. Nous considerons les couches poreuses de C et BN basees sur le graphene et l'α-graphyne. Nous trouvons que le graphene poreux est un isolant, alors que l'α-graphyne a des proprietes semi-conductrices. La substitution d'atomes de C par des atomes de B et N elargit la bande interdite. Les couches BN de type graphene poreux et de type graphyne poreux se comportent comme des isolants. La bande interdite non nulle des couches de C et de BN peut constituer une opportunite pour utilisation dans des dispositifs nanoelectroniques. [Traduit par la Redaction] Mots-cles : graphene poreux, graphyne poreux, couche de BN, propriete electronique, theorie de la fonctionnelle de densite. PACS Nos.: 31.15.E, 61.48.Gh., 1. Introduction Graphene (G), a monolayer hexagonal structure of C atoms, exhibits potential applications in many fields [1]. The numerous applications of G are mainly due to its unique electronic [...]

The spectroscopic properties of poly (styrene-co-p-vinylbenzyl chloride) (poly (St-co-VBC)) were investigated by Fourier transform infrared spectroscopy and *H nuclear magnetic resonance spectroscopic techniques. The molecular geometry and vibrational frequencies of macroinitiator, poly (St-co-VBC), were calculated by using density functional theory (DFT) and Hartree-Fock (HF) methods with 6-31 G+ (d, p) as a basis set. Calculated theoretical values are shown to be in good agreement with that of experimental values. An excellent harmony between the two data sets was verified. Besides, the experimental data of macroinitiator were compared with experimental data of its corresponding monomers such as St and VBC. The dimer and trimer forms of macroinitiator are used as significant contributions for getting an accurate interpretation of the experimental frequencies of poly (St-co-VBC). The results revealed that the change from St and VBC to poly (St-co-VBC) should be characterized by the disappearance of the C[H.sub.2]=CH bonds of the vinyl group and the appearance of the aliphatic C-H and C[H.sub.2] bonds. The geometrical parameters, Mulliken atomic charges and frontier molecular orbitals energies were also calculated using the same theoretical methods. The chemical shifts were calculated by using the gauge-including atomic orbital method and all the theoretically predicted values were shown to be in good agreement with experimental values. Molecular orbital properties, molecular electrostatic potential, and the potential energy surface for the atom transfer radical polymerization (ATRP) of the macroinitiator were studied with DFT and HF calculations. The potential energy surface of the ATRP initiator is decided by their electronic effect and steric hindrance effect simultaneously. Key words: styrene, p-vinylbenzyl chloride (VBC), macroinitiator, vibrational spectra, DFT, MEP, FMOs, ATRP. Nous etudions les proprietes spectroscopiques du poly (p-chlorure de venylbenzyl-co-styrene) (poly (St-co-VBC)) a l'aide des techniques de spectroscopie infrarouge a transformee de Fourier et de spectroscopie de RMN sur 1H. La geometrie moleculaire et les frequences vibrationnelles du macro-amorceur poly (St-co-VBC) sont calculees a partir des methodes de la fonctionnelle de densite (MFD) et de Hartree-Fock (HF) dans un espace de base 6-31G+ (d, p). Les valeurs calculees sont en bon accord avec les valeurs experimentales. Nous constatons une excellente harmonie entre les deux. De plus, nous comparons les valeurs experimentales du macro-amorceur avec les valeurs experimentales de ses monomeres, St et VBC. Les formes dimere et trimere du macro-amorceur contribuent significativement a une description precise des frequences experimentales du poly (St-co- VBC). Les resultats montrent que le changement de St et VBO a poly (St-co-VBC) apparait etre caracterise par la disparition des liens C[H.sub.2]=CH du groupe vinyle et l'apparition des liens aliphatiques C-H et C[H.sub.2]. Les parametres geometriques, les charges atomiques de Mulliken et les energies FMO sont calcules par les memes methodes theoriques. Les deplacements chimiques sont calcules en utilisant la methode des orbitales atomiques incluant les effets de jauge et nous montrons que toutes les valeurs theoriques sont en bon accord avec les valeurs experimentales. De plus, les proprietes des orbitales moleculaires, le potentiel electrostatique moleculaire et l'analyse des surfaces d'energie potentielle pour l'ATRP du macro-amorceur sont etudies par calculs MFD et HF et la surface d'energie potentielle de l'amorceur ATFP est fixee simultanement par leur effet electronique et leur encombrement sterique. [Traduit par la Redaction] Mots-cles : styrene, p-chlorure de venylbenzyl (VBC), macro-amorceur, spectres de vibration, DFT, MEP, FMOs, ATRP. PACS Nos.: 31.15.A, 31.15.ae, 31.15.at, 31.15.E-, 33.20.Tp., 1. Introduction Polymerization reactions involving a macroinitiator have aroused great interest because of the wide possibilities for the preparation of new polymeric materials. A popular and important controlled radical polymerization [...]

An ab initio calculation of the structural, elastic, and electronic properties of indium arsenide (InAs) under induced pressure is investigated using density functional theory with modified Becke-Johnson potential within the generalised gradient approximation of the Perdew-Burke-Ernzerhof scheme. The lattice parameters are found to be in good agreement with experimental and other theoretical data. The pressure-induced structural phase transition of InAs zinc blende to rock salt structure is found to occur at 4.7 GPa pressure with a 17.2% of volume collapse. The elastic properties of both the zinc blende and rock salt structures at different pressures are studied. The electronic band structures at different pressures for both the structures are investigated using the total and partial density of states. The energy band gap of the InAs zinc blende phase is increased with increasing pressure while in rock salt the phase the conduction band crosses towards the valence band and thus shows metallic behaviour. Key words: density functional theory (DFT), modified Becke-Johnson (mBJ) potential, density of states (DOS), energy band diagram, elastic properties, phase transition. Nous presentons un calcul ab initio des proprietes structurelles, elastiques et electroniques de l'arseniure d'indium (InAs) sous pression, a l'aide de la theorie de la fonctionnelle de densite avec un potentiel modifie de Becke-Johnson, a l'interieur de l'approximation du gradient generalise du schema de Perdew-Burke-Ernzerhof. Nous trouvons que les parametres du reseau sont en bon accord avec les donnees experimentales et d'autres resultats theoriques. Nous trouvons que la transition de phase de InAs induite par la pression, de la phase blende de zinc a sel gemme se produit a 4.7 GPa, avec diminution de volume de 17.2 %. Nous etudions les proprietes elastiques des structures blende de zinc et sel gemme en utilisant les densites d'etat, totale et partielle. La bande en energie interdite du blende de zinc croit avec l'augmentation de pression, alors que dans la phase sel gemme la bande de conduction traverse vers la bande de valence et montre ainsi de meilleures proprietes metalliques. [Traduit par la Redaction] Mots-cles : theorie de la fonctionnelle de densite, diagramme de la bande d'energie, densite d'etats, proprietes elastiques, transition de phase. PACS Nos.: 71.15.Mb, 71.20.-b;71.20.Nr., 1. Introduction The technological importance of group III-V compound semiconductors has increased over the past years because of its electronic and mechanical properties and has received considerable interest from experimentalist [...]

In this work, we conducted a systematic search of the minimum energy of a dopamine-β-cyclodextrin complex via different ONIOM approaches using both mixed (DFT-HF) and nonmixed (DFT-DFT) combinations. Different density functionals were employed: B3LYP, MPW1PW91, M05-2X, M06-2X, and mB97X-D. Two different basis sets were used on the dopaminepcyclodextrin complex; a lower basis set (3-21[G.sup.*]) is used on β-cyclodextrin and a higher basis set (6-31G(d)) is used on dopamine. To fulfill this task, complexation and deformation energies were determined. The relative performance of these functionals was compared with that obtained with the DFT method at the M06-2X/6-31G(d) level that is chosen as a reference method. Although we did not clearly establish an assessment of the relative performance of these density functionals, the efficacy of the ONIOM combination (DFT-HF) is shown compared with a nonmixed ONIOM combination (DFT-DFT). The intermolecular hydrogen bond interactions of the complex obtained with the full M06-2X/6-31G(d) have been analyzed with the atoms-in-molecules and natural bond rrbital methodologies. Key words: dopamine, p-cyclodextrin, inclusion complexes, ONIOM2, DFT. Dans le cadre de ces travaux, nous avons realise une recherche systematique de l'energie minimale d'un complexe de dopamine-β-cyclodextrine au moyen de differentes approches ONIOM en utilisant la combinaison mixte (DFT-HF) et la combinaison non mixte (DFT-DFT). Nous avons employe differentes fonctionnelles de la densite : B3LYP, MPW1PW91, M05-2X, M06-2X et mB97X-D. Deux bases differentes ont ete utilisees pour le complexe dopamine-β-cyclodextrine, une base inferieure (321[G.sup.*]) pour la β-cyclodextrine et une base superieure (6-31G(d)) pour la dopamine. Afin d'accomplir cette tache, nous avons determine les energies de complexation et de deformation. Nous avons compare la performance relative de ces fonctionnelles a celle qui etait obtenue par la methode DFT au niveau M06-2X/6-31G(d) que nous avons choisie comme methode de reference. Bien que nous n'ayons pas clairement etabli d'evaluation de la performance de ces fonctionnelles de la densite, nous presentons l'efficacite de la combinaison ONIOM (DFT-HF) par rapport a une combinaison ONIOM non mixte (DFT-DFT). Nous avons analyse les interactions intermoleculaires produites par les liaisons hydrogene dans le complexe, que nous avons obtenues au niveau M06-2X/6-31G(d) complet avec les methodes de la theorie quantique des atomes dans les molecules et de la theorie des orbitales naturelles de liaison. [Traduit par la Redaction] Mots-cles : dopamine, p-cyclodextrine, complexes d'inclusion, ONIOM2, DFT., Introduction Supramolecular chemistry, a combination of two or more species, is based on noncovalent interactions, which are the source of several highly specific processes. These processes occur in biology such [...]

The electronic, mechanical, and thermodynamic properties of europium carbide (Eu[C.sub.2]) are investigated using first-principles density functional theory within the generalized gradient approximation. The calculated elastic constants indicate that Eu[C.sub.2] is mechanically stable. The shear modulus, Young's modulus, Poisson's ratio, the bulk modulus--shear modulus ratio, shear anisotropy, and elastic anisotropy are also calculated. Finally, we obtain the Vickers hardness, averaged sound velocity, longitudinal sound velocity, transverse sound velocity, Debye temperature, melting point, and thermal conductivity of Eu[C.sub.2]. PACS Nos.: 62.20.F-, 62.20.de, 31.15.E-. Nous analysons les proprietes electroniques, mecaniques et thermodynamiques du carbure d'europium (Eu[C.sub.2]) en utilisant la theorie ab initio de la fonctionnelle de densite dans l'approximation du gradient generalise. Les constantes elastiques calculees indiquent que Eu[C.sub.2] est mecaniquement stable. Nous calculons aussi le module de cisaillement, le module de Young, le rapport de Poisson, le rapport, l'anisotropie de cisaillement et l'anisotropie elastique. Finalement, nous obtenons la durete de Vickers, la vitesse moyenne du son, la vitesse du son longitudinal, la vitesse du son transversal, la temperature de Debye, le point de fusion et la conductivite thermique. [Traduit par le Redaction], 1. Introduction Rare-earth (RE) metal carbides are composed of a RE metal ion and a carbon ion. Depending on the RE metal, their physical properties may vary over a wide [...]

A theoretical study of Pb(II) square planar thioselenophosphinate, Pb[[[([C.sub.6][H.sub.5]).sub.2]PSSE].sub.2] precursor for the chemical vapour deposition process of preparing lead chalcogenides, has been carried out. The geometries of the species were optimized by employing the density functional theory. The transition states as well as the linked intermediates linking them were confirmed with frequency analyses. The density functional theory calculation (M06/LACVP*, gas) reveals that kinetically, the steps that lead to PbSe formation are more favourable than those that lead to PbS and ternary Pb[Se.sub.x][S.sub.1-x] formation on both the singlet and the doublet potential energy surface. However, thermodynamically, the steps that lead to ternary Pb[Se.sub.x][S.sub.1-x] formation are more favourable than those that lead to PbSe and PbS formation on the doublet potential energy surface. On the singlet potential energy surface, an alternative route leading to the formation of ternary Pb[Se.sub.x][S.sub.1-x] is more favoured on both thermodynamic and kinetic grounds than those that lead to PbSe and PbS formation. The computational studies indicate that the decomposition of the complex in chemical vapour deposition may involve more than one step, and thus the formation of ternary Pb[Se.sub.x][S.sub.1-x] is a result of thermodynamic and kinetic factors in controlling the material formed during the deposition process. Key words: density functional theory, thioselenophosphinate, lead, chalcogenides, chemical vapour deposition. On a realise l'etude theorique du thioselenophosphinate plan carre de Pb(II), Pb[[[([C.sub.6][H.sub.5]).sub.2]PSSE].sub.2], precurseur du procede de synthese de chalcogenures de plomb par depot chimique en phase vapeur. Les geometries des especes en presence ont ete optimisees au moyen de la theorie de la fonctionnelle de la densite. Les etats de transition et les intermediaires les reliant entre eux ont ete connectes ont ete confirmes par des analyses de frequence. Les calculs de la theorie de la fonctionnelle de la densite (M06/LACVP*, gaz) revelent que, sur le plan cinetique, les etapes qui conduisent a la formation de PbSe sont plus favorisees que celles conduisant a la formation de PbS et de Pb[Se.sub.x][S.sub.1-x] ternaire sur les surfaces d'energie potentielle du singulet et du doublet. Cependant, sur le plan thermodynamique, celles qui menent a la formation de Pb[Se.sub.x][S.sub.1-x] ternaire sont plus favorisees que celles menant a la formation de PbSe et de PbS formation sur la surface d'energie potentielle du doublet. Sur la surface d'energie potentielle du singulet, une autre voie reactionnelle conduisant a la formation de Pb[Se.sub.x][S.sub.1-x] ternaire est favorisee du point de vue thermodynamique et cinetique par rapport a celle qui conduit a la formation de PbSe et de PbS formation. Les etudes computationnelles indiquent que la decomposition du complexe lors depot chimique en phase vapeur pourrait comporter plus d'une etape et que la formation de Pb[Se.sub.x][S.sub.1-x] ternaire serait donc le resultat de l'influence de facteurs thermodynamiques et cinetiques sur le produit forme au cours du processus de depot. [Traduit par la Redaction] Mots-cles: theorie de la fonctionnelle de la densite, thioselenophosphinate, plomb, chalcogenures, depot chimique en phase vapeur., Introduction Metal dichalcogenophosphinates represent an important class of organophosphorus compounds that are widely used both in industry and academic research. (1) Structural information such as geometrical and electronic configurations, molecular [...]

In the present study, the density functional method with recently developed M06 functionals has been used to study the reaction of C[F.sub.3]OC[H.sub.2]C[H.sub.3] with the OH radical. All possible hydrogen abstraction and displacement reaction channels have been modeled. The minimum energy path on the respective potential energy surface and energetics were calculated at the M06-2X/6-311++G(d,p) level of theory. Two different reaction mechanisms were considered: (i) reactant and product complexes called the complex mechanism and (ii) the direct mechanism (reactant [right arrow] transition state → product). Tunneling corrections were made using the Eckart unsymmetrical potential. The overall rate constant calculated by the complex mechanism ([k.sub.eff] = 1.8 x [10.sup.-13] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]) has been found to be in good agreement with the experimentally determined value (1.5 ± 0.25 x [10.sup.-13] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]), while the rate constant calculated by the direct mechanism ([k.sub.D] = 7.6 x [10.sup.-14] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]) is about two times lower than the experimental value. The theoretical studies show that hydrogen atom abstraction from the - C[H.sub.2]- site is the most favorable reaction pathway and the reaction involves prereactive and product complexes before leading to stable product formation. Key words: kinetics, density functional theory, tunneling, potential energy surface. Dans le cadre de la presente etude, nous avons utilise la methode de la fonctionnelle de la densite avec les fonctionnelles M06 recemment developpees afin d'etudier la reaction du C[F.sub.3]OC[H.sub.2]C[H.sub.3] avec le radical OH. Nous avons modelise tous les canaux possibles d'arrachement d'hydrogene et de reactions de deplacement. La voie reactionnelle d'energie minimale sur la surface d'energie potentielle respective et l'energetique ont ete calculees au niveau M06-2X/6-311++G(d,p) de la theorie. Nous avons considere deux mecanismes de reaction differents: (i) un mecanisme faisant intervenir des complexes de reactifs et de produits, appele mecanisme de complexes, et (ii) le mecanisme direct (reactif → etat de transition → produit). Les corrections pour tenir compte de l'effet tunnel ont ete apportees en utilisant le potentiel asymetrique d'Eckart. Nous avons constate que la constante de vitesse globale calculee pour le mecanisme de complexes ([k.sub.ef] = 1,8 x [10.sup.-13] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]) concordait bien avec la valeur determinee en conditions experimentales (1,5 ± 0,25 x [10.sup.-13] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]), tandis que la constante de vitesse calculee pour le mecanisme direct ([k.sub.D] = 7,6 x [10.sup.-14] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]) etait environ deux fois plus basse que la valeur experimentale. Les etudes theoriques montrent que l'arrachement d'un atome d'hydrogene du radical -C[H.sub.2]- est la voie reactionnelle la plus favorable et que la reaction fait intervenir des complexes avant et apres la reaction prealablement a la formation d'un produit stable. [Traduit par la Redaction] Mots-cles: cinetique, theorie de la fonctionnelle de la densite, effet tunnel, surface d'energie potentielle., Introduction It is now a well-established fact that chlorofluorocarbons (CFCs) are a major threat for the depletion of the ozone layer in the stratospheric region of the atmosphere. (1-3) Such [...]

The switchable second-order nonlinear optical properties of a series of dithienylethene-containing boron compounds possessing reversible photochromic behavior have been systemically investigated based on density functional theory. The significant differences on the static first hyperpolarizabilities caused by the photoisomerization reaction confirm the switchable nonlinear optical behavior. Results show that the closed-ring 1c-4c possess large static first hyperpolarizabilitieswith respect to their corresponding open-ring 1o-4o, which is due to the better π-conjugation and a more obvious degree of charge transfer. Specifically, the static first hyperpolarizability values increase in the range of 2.4-5.2 times with the strengthening electronwithdrawing ability of the substituent R (R = H, C[F.sub.3], N[O.sub.2]) on the pyridine and elongating the conjugated chains. It indicates that introducing boron-based functional groups to the dithienylethene monomer and modifying the pyridine ring can effectively improve the switching nonlinear optical responses. Key words: dithienylethene, boron compounds, photoisomerization, second-order nonlinear optical property. Les proprietes optiques non lineaires de second ordre commutables d'une serie de composes de bore contenant du dithienylethene et presentant un photochromisme reversible ont ete methodiquement etudiees a partir de la theorie de la fonctionnelle de la densite. Les differences importantes au niveau des premieres hyperpolarisabilites statiques, causees par les reactions de photoisomerisation, confirment les proprietes optiques non lineaires commutables. Les resultats montrent que les cycles fermes 1c-4c presentent des premieres hyperpolarisabilites statiques importantes en lien avec leurs cycles ouverts correspondants, 1o-4o, en raison d'une meilleure conjugaison n et d'un meilleur degre apparent de transfert de charge. D'une maniere plus specifique, la valeur de premieres hyperpolarisabilites statiques augmente d'un facteur compris entre 2,4 et 5,2 lorsque le caractere electrophile du substituant R (R = H, CF3, NO2) present sur la pyridine augmente et lorsque les chaines conjuguees s'allongent. Ceci montre que l'introduction de groupes fonctionnels composes de bore dans le monomere de dithienylethene et la modification du cycle pyridine peuvent efficacement augmenter les phenomenes optiques non lineaires de commutation. [Traduit par la Redaction] Mots-cles: dithienylethene, composes de bore, photoisomerisation, propriete optique non lineaire de second ordre., Introduction Organic nonlinear optical (NLO) materials have attracted considerable attention because they have many possible advantages relative to conventional inorganic crystalline materials. (1-3) Especially organic and reversible molecular switches have [...]

The generalized gradient approximation of density functional theory was used to investigate the adsorption and dissociation of a single isopropyl nitrate molecule on an Al(111) surface. The isopropyl nitrate tends to adsorb in a parallel mode with respect to the Al(111) surface. A total of 10 dissociation modes were investigated including both the vertical and parallel dissociations. The analysis of transition states, density of states, and the Hirshfeld populations have been carried out. In general, the dissociations on the same site would produce similar products. The surface aluminum atoms would attract the oxygen or nitrogen atoms dissociated from the nitro group, leading to the formation of three Al-O or Al-N bonds on the surface. Our study presented a deep insight into the dissociation behaviors as well as the mechanisms of isopropyl nitrate on the aluminum surface. Moreover, the smallest activation barrier energy for the isopropyl nitrate dissociation on the aluminum surface is 58.51 kJ/mol, which is much lower than that of 158 kJ/mol for the direct decomposition. Key words: isopropyl nitrate, Al(111) surface, adsorption, decomposition, density functional theory. Au moyen de l'approximation des gradients generalisee de la theorie de la fonctionnelle de la densite, nous avons etudie l'adsorption et la dissociation moleculaire d'une molecule unique de nitrate d'isopropyle sur une surface d'Al(111). Le nitrate d'isopropyle a tendance a s'adsorber parallelement a la surface d'Al(111). En tout, 10 modes de dissociation ont ete etudies, y compris les dissociations verticales et paralleles. Les analyses des etats de transition, de la densite des etats electroniques, ainsi que des populations de Hirshfeld ont ete effectuees. Generalement, les dissociations au meme endroit devraient mener a la formation de produits semblables. Les atomes de la surface d'aluminium devraient attirer les atomes d'oxygene et d'azote dissocies du groupement nitro, entrainant la formation de trois liaisons Al-O ou Al-N sur la surface. Notre etude pose un regard approfondi sur les comportements du nitrate d'isopropyle sur une surface d'aluminium ainsi que sur ses mecanismes de dissociation de cette surface. En outre, la plus petite barriere d'energie d'activation de la dissociation du nitrate d'isopropyle est de 58,51 kJ/mol, une valeur nettement inferieure a celle de la decomposition directe, qui est de 158 kJ/mol. [Traduit par la Redaction] Mots-cles: nitrate d'isopropyle, surface d'Al(111), adsorption, decomposition, theorie de la fonctionnelle de la densite., Introduction Due to the high reducibility, metal has always been considered as one very important additive in propellant formulations to improve the performance of high energetic ingredients. Powdered aluminum is [...]

We investigated the heat of formation, density, thermal stability, and detonation properties of a series of carbonoxidized triazole and tetrazole derivatives substituted by -N[H.sub.2] and -N[O.sub.2] groups using density functional theory. It is found that their properties are associated with the numbers of substituents and substitution positions in the parent ring. The results show that the -N[O.sub.2] group is an effective structural unit for enhancing their detonation performance. It also indicates that the substitution positions play a very important role in increasing the heat of formation values of the derivatives. An analysis of impact sensitivity ([h.sub.50]) indicates that incorporating the -N[H.sub.2] groups into the parent ring increases their thermal stability. Considering the detonation performance and thermal stability, seven of the designed compounds may be regarded as potential high-energy compounds. These results provide basic information for the molecular design of novel high-energy compounds. Key words: density functional theory, carbon-oxidized triazole and tetrazole derivatives, heat of formation, detonation properties, impact sensitivity. Au moyen de la theorie de la fonctionnelle de la densite, nous avons etudie la chaleur de formation, la densite, la stabilite thermique ainsi que les proprietes de detonation d'une serie de derives de triazoles et de tetrazoles oxydes en position carbonee et substitues par des groupements -N[H.sub.2] et -N[O.sub.2]. Nous constatons que les proprietes de ces derives dependent du nombre de substituants et de leur position sur le noyau de la molecule mere. Les resultats revelent que le groupement - N[O.sub.2] est une unite structurelle qui permet d'ameliorer efficacement le pouvoir de detonation. Ils indiquent egalement que les positions de substitution jouent un role tres important dans l'accroissement des valeurs de la chaleur de formation des derives. Une analyse de la sensibilite au choc ([h.sub.50]) indique que l'incorporation de groupements -N[H.sub.2] au noyau de la molecule mere ameliore la stabilite thermique de celui-ci. Etant donne leur pouvoir de detonation et de leur stabilite thermique, sept des composes a l'etude peuvent etre consideres comme des molecules a potentiel energetique eleve. Ces resultats fournissent des renseignements fondamentaux utiles a la creation de nouvelles molecules a potentiel energetique eleve. [Traduit par la Redaction] Mots-cles: theorie de la fonctionnelle de la densite, derives de triazoles et de tetrazoles oxydes en position carbonee, chaleur de formation, proprietes de detonation, sensibilite au choc., Introduction Energetic nitrogen-rich heterocyclic compounds are promising candidates for high-energy density compounds (HEDCs) due to a high positive heat of formation (HOF), high density, acceptable oxygen balance (OB), and excellent [...]

Using the self-consistent density functional method, we investigate the structural and electronic properties of cubic [Hf.sub.3][N.sub.4] with [Th.sub.3][P.sub.4] structure at ambient and high pressures. The lattice parameters, cell volume, bulk modulus, and pressure derivative at ambient pressure are obtained, which are in excellent agreement with the available measurements. The change of bond lengths for two different types of Hf-N bond with pressure suggests that the tetrahedral Hf-N bond is slightly less compressible than the octahedral ones, which agree well with the [Zr.sub.3][N.sub.4] and [Zn.sub.3][N.sub.2] results. The band gap pressure coefficient for c-[Hf.sub.3][N.sub.4] are fitted, which are 8.5 x [10.sup.-2] eV/GPa and -7.0 x [10.sup.-5] eV/[(GPa).sup.2], respectively. Based on the density of states analysis, band structure suggests that the investigated material can be used as a semiconductor optical material. Mulliken population analysis shows that the charge density of the Hf atom is less sensitive to pressure variation than that of the N atom. At last, the defect formation enthalpies of the cubic [Hf.sub.3][N.sub.4] are calculated. PACS Nos.: 62.50.-p, 71.15.Mb, 73.20.At. L'utilisation de la methode de la fonctionnelle de densite auto-coherente nous permet d'etudier les proprietes structurelles et electroniques du [Hf.sub.3][N.sub.4] cubique avec la structure [Th.sub.3][P.sub.4] a pression ambiante et haute. Nous obtenons les parametres du reseau, le volume de la cellule, le module de compression volumique et la derivee de la pression, le tout a pression ambiante et ces resultats sont en excellent accord avec les mesures disponibles. La variation avec la pression de la longueur de lien entre deux liens Hf-N differents suggere que le lien Hf-N tetraedrique est legerement moins compressible que l'octaedrique, ce qui agree avec les resultats pour [Zr.sub.3][N.sub.4] et [Zr.sub.3][N.sub.2]. Les coefficients de pression de la bande interdite de c-[Hf.sub.3][N.sub.4] sont alors ajustes numeriquement: 8.5 x [10.sup.-2] eV/GPa et -7.0 x [10.sup.-5] eV/GPa respectivement. Sur la base de l'analyse de la densite d'etats, la structure de bande suggere que ce materiau peut etre utilise comme semi-conducteur optique. L'analyse des charges de Mulliken montre que la densite de charge de l'atome Hf est moins sensible aux variations de pression que celle de l'atome N. Finalement, nous calculons l'enthalpie de formation de defauts dans [Hf.sub.3][N.sub.4] cubique. [Traduit par la Redaction], 1. Introduction Nitrides of transition metals that are used as hard materials have attracted great interest because of their high elastic moduli, ultrahardness, high melting points, and superconductivity [1-5]. Novel [...]

Investigations into the electronic properties, elastic properties, and ideal tensile strengths for [Ti.sub.2]AlN and [Ti.sub.4]Al[N.sub.3] were conducted using first-principles density functional calculations. The electronic band structures and density of states show metallic conductivity in which Ti 3d states dominate for [Ti.sub.2]AlN and [Ti.sub.4]Al[N.sub.3]. Moreover, the hybridization peak of Ti 3d and N 2p lies at a lower energy than that of Ti 3d and Al 3p, which suggests that the Ti 3d - N 2p bond is stronger than the Ti 3d - Al 3p bond. The variations of elastic constants with pressure indicate that [Ti.sub.2]AlN and [Ti.sub.4]Al[N.sub.3] possess higher mechanical stability in the pressure range 0-100 GPa. By calculating the bulk-modulus-to-shear-modulus ratio and Cauchy pressure, we predict that [Ti.sub.2]AlN and [Ti.sub.4]Al[N.sub.3] are brittle. We show that the structural failure of these ternary compounds can be ascribed to the breakage of weak Ti-Al bonds under uniaxial tension and that layered structural stability is determined by the strength of the Ti-Al bond under tensile deformation. PACS Nos.: 71.15.Mb, 62.20.de, 74.62.Fj. Utilisant une approche de principes premiers et la methode de la fonctionnelle de densite, nous calculons les proprietes electroniques et elastiques, ainsi que la resistance a la traction dans des echantillons de [Ti.sub.2]AlN et de [Ti.sub.4]Al[N.sub.3]. Les structures des bandes electroniques et la densite d'etats indiquent une conductivite electrique dans laquelle dominent les etats 3d du Ti pour les deux types d'echantillon. De plus, le pic d'hybridation du 3d du Ti et du 2p de N est plus bas en energie que celui du 3d du TI et du 3p de Al. La variation des constantes elastiques avec la pression montre que [Ti.sub.2]AlN et [Ti.sub.4]Al[N.sub.3] ont une plus grande stabilite mecanique sous des pression dans le domaine 0-100 GPa. En calculant le rapport du module de compression en volume sur le module de cisaillement et la pression de Cauchy, nous predisons que [Ti.sub.2]AlN et [Ti.sub.4]Al[N.sub.3] sont fragiles sous traction. Nous montrons que la cause de la defaillance structurelle dans ces composes ternaires est due au bris du lien Ti-Al sous traction uniaxiale et la stabilite de la structure en couches est determinee par la force du lien Ti-Al dans la deformation sous traction. [Traduit par la Redaction], 1. Introduction [M.sub.n+1]A[X.sub.n] compounds (where M is an early transition metal, A is an A-group element, X is C or N, and n = 1-3) have attracted attention owing to [...]

Nitrogen-rich 1,2,4-triazole (1) and 1,2,3-triazole (2) react as bases with the oxygen-rich acids HN[O.sub.3] (a), HN[(N[O.sub.2]).sub.2] (b), and HCl[O.sub.4] (c) to produce energetic salts (1a, 1b, and 1c and 2a, 2b, and 2c, respectively) potentially applicable to composite explosives and propellants. In this study, these salts were studied with the dispersion-corrected density functional theory. For the isomers such as 1a and 2a, the more negative [Δ.sub.r][G.sub.m] of the formation reaction leads to a higher thermally stable salt. The ability to form intramolecular hydrogen bonds predicted with the quantum theory of atoms in molecules has the order of 2 > 1. Different hydrogen bonds result in different second-order perturbation energies, redshifts in IR, and electron density differences. The charge transfer, binding energy, dispersion energy, lattice energy, and energy gap between frontier orbits in the salts of 1 are larger than those of 2, which is helpful for stabilizing the former, and 1 is more obviously stabilized than 2 by formation of salts. Different conformations of 1 and 2 hardly affect the frontier orbital distributions. Base 1 is a more preferred base than 2 to form salts. Key words: 1;2;3- and 1;2;4-triazoles, stability, hydrogen bonds, intramolecular interaction, quantum chemistry. Le 1,2,4-triazole (1) et le 1,2,3-triazole (2), tous deux riches en azote, reagissent en tant que bases avec les acides HN[O.sub.3] (a), HN[(N[O.sub.2]).sub.2] (b) et HCl[O.sub.4] (c) riches en oxygene pour produire des sels energetiques (1a, 1b et 1c et 2a, 2b et 2c respectivement) pouvant entrer dans la composition d'explosifs et d'agents propulsifs. Dans la presente etude, ces sels ont ete etudies a l'aide de la theorie de la fonctionnelle de la densite avec correction de dispersion. Dans le cas des isomeres tels 1a et 2a, la valeur plus negative de l'enthalpie libre [Δ.sub.r][G.sub.m] de la reaction de synthese conduit a la formation de sels a haute stabilite thermique. La capacite de ces derniers a former des liaisons hydrogenes predite a l'aide de la theorie quantique des atomes dans les molecules suit l'ordre 2 > 1. Differentes liaisons hydrogenes donnent lieu a des energies de perturbation du deuxieme ordre differentes, des decalages vers le rouge dans l'IR et des differences de densite electronique. Le transfert de charge, l'energie de liaison, l'energie de dispersion, l'energie reticulaire et l'ecart d'energie entre les orbitales frontieres dans les sels de 1 sont superieurs a ceux des sels de 2, ce qui aide a stabiliser les premiers. De plus, 1 est encore plus stabilise que 2 par la formation de sels. Differentes conformations de 1 et de 2 n'affectent pratiquement pas la distribution des orbitales frontieres. Il est preferable d'utiliser la base 1 plutot que la base 2 pour former des sels. [Traduit par la Redaction] Mots-cles: 1;2;3-triazole et 1;2;4-triazole, stabilite, liaisons hydrogenes, interaction intramoleculaire, chimie quantique., Introduction Energetic materials are widely used for propelling missiles and rockets and for blasting, mining, cratering, and other civil engineering purposes. (1-7) When a very high rate of energy output [...]