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How to search for a convenient method without a complicated calculation process to predict the physicochemical properties of inorganic crystals through a simple micro-parameter is a greatly important issue in the field of materials science. Herein, this paper presents a new and facile technique for the comprehensive estimation of lattice energy (U), bulk modulus (B), chemical hardness (ƞ), and electronic polarizability (α), just by using a simple mathematic fitting formula with a few structure parameters, such as the systems of rock salt crystals (group I–VII, II–VI) and tetrahedral coordinated crystals (group II–VI, III–V). For the typical binary ANB8-N crystal systems, our present conclusions suggest that a good quantitative correlation between U, B, ƞ, α and chemical bond length (d) is observed, the normal mathematical expression is P = a·db (P represents these physicochemical parameters), constants a and b depend on the type of crystals, and the relevant squares of the correlation coefficient (R2) are larger than 0.9. The results indicate that lattice energy, bulk modulus, and chemical hardness decrease with increases in chemical bond length, but electronic polarizability increases with an increase in chemical bond length. Meanwhile, the new data on the lattice energy, bulk modulus, chemical hardness, and electronic polarizability values of binary ANB8-N crystal systems considered in the present study are calculated via the obtained curve fitting equations without any complex calculation process. We find that there is a very good linear trend in our calculated results along with the values reported in the literature. The present study will be important in solid-state chemistry, which may give researchers useful guidance in searching for relevant data for predicting the properties of new materials or synthetic routes based on a simple mathematic empirical model.

The inhibitory effect of MgO, FeO, CaF2, and Al2O3 additive on the dissolution of Ca into water from 10 quasi-ternary silicate mineral phases was studied according to the silicate crystal structure. After adding MgO or FeO, the dissolution ratio of Ca decreased by Ca2+ substitution with Mg2+ or Fe2+. In the CaF2-added silicate phase Ca4Si2O7F2, non-existence of the face-sharing type of linkage between CaOx polyhedrons could be a reason for the low dissolution ratio of Ca. In Al2O3-containing silicates, Al atoms could form [AlO4]5− and [AlO6]9− polyhedrons linked to [SiO4]4− tetrahedrons to form a complicated silicate network structure with a higher polymerization degree, which helps suppress the dissolution of Ca. The dissolution ratio of Ca is also inversely correlated to the overall polymerization degree in the silicate network structure. Using multivariate analysis, the dissolution ratio of Ca was predicted utilizing factors internal to the silicate structure (corrected basicity, polymerization degree of silicate network structure, lattice energy, and average nearest neighbor Ca–O distance). For both quasi-binary and quasi-ternary systems, the overall polymerization degree of silicate network strongly affects the dissolution of Ca, while the other factors only make slight contributions.

The objective of this study is to investigate the energy absorption performance of the graded lattice energy absorbers designed by a stiffness-based size optimization process under static loadings applied during the in-service conditions. The energy absorber geometry is modeled using three different lattice types, namely complex cubic, octet cubic, face- and body-centered cubic. The stiffness-based size optimization subjected to a static bending load is conducted to determine the optimal strut diameters which produced graded lattice structure designs. To investigate the energy absorption behavior of these graded lattice designs, the nonlinear dynamic explicit finite element analysis (FEA) is conducted under quasi-static compression for each design. The lattice designs are fabricated by a material extrusion technique using the polylactic acid material and the quasi-static uniaxial compression tests are conducted on the fabricated designs. The FEA results are found to be in good agreement with the experimental results. When compared with uniform counterparts, the presented graded lattices exhibit the improved energy absorption in response to uniaxial compression although their designs were derived from a stiffness-based size optimization with bending load.

A phenomenological model of anisotropic lattice vibrations is proposed, using a temperature-dependent spectral cutoff and varying Debye temperatures for the vibrational normal components. The internal lattice energy, entropy and Debye–Waller B factors of non-cubic elemental crystals are derived. The formalism developed is non-perturbative, based on temperature-dependent linear dispersion relations for the normal modes. The Debye temperatures of the vibrational normal components differ in anisotropic crystals; their temperature dependence and the varying spectral cutoff can be inferred from the experimental lattice heat capacity and B factors by least-squares regression. The zero-point internal energy of the phonons is related to the low-temperature limits of the mean-squared vibrational amplitudes of the lattice measured by X-ray and γ-ray diffraction. A specific example is discussed, the thermodynamic variables of the hexagonal close-packed zinc structure, including the temperature evolution of the B factors of zinc. In this case, the lattice vibrations are partitioned into axial and basal normal components, which admit largely differing B factors and Debye temperatures. The second-order B factors defining the non-Gaussian contribution to the Debye–Waller damping factors of zinc are obtained as well. Anharmonicity of the oscillator potential and deviations from the uniform phonon frequency distribution of the Debye theory are modeled effectively by the temperature dependence of the spectral cutoff and Debye temperatures.

The structures and interactions in four new hydrates of substituted piperidines have been studied using X-ray crystallography and quantum chemistry. The piperidine ring substitution leads to a significant reduction in the number of hydrates compared with the parent amine, with 4-methylpiperidine yielding a hemihydrate and a trihydrate; 4-chloropiperidine a monohydrate and a trihydrate, (where the architecture is similar to 4-methylpiperidine trihydrate). Despite many attempts, it did not prove possible to crystallize hydrates with higher molar amine : water ratios. Therefore, trihydrates are probably the most hydrated crystals to be obtained at ambient pressure for both amines. Both trihydrates create identical water layers of the L4(6)5(7)6(8) type and the main structural difference is the arrangement of hydrogen bonds between water layers and amines. Despite this, both trihydrates have the same melting temperature (263 K) and as supported by lattice energy calculations. Chlorine⋯chlorine contacts have no significant impact on the stabilization of the 4-chloropiperidine monohydrate or the 4-chloropiperidine trihydrate. Periodic DFT-D3 calculations show that the energies of the water layers are identical in both cases, and the summed hydrogen bond energies (although arranged differently) are similar. Moreover, in the case of trihydrates, which have a 2-D topology of water⋯water interactions, it is possible to perform DFT calculations for separate layers and to determine the contribution of those interaction energies to the cohesive energy of the whole crystals.

9-Anthracene carboxylic acid derivatives comprise a family of thermally reversible photomechanical molecular crystals. The photomechanical response relies on a [4 + 4] photodimerization followed by dissociation that occurs on timescales of seconds to minutes. A combined theoretical and experimental investigation is undertaken to better understand how chemical modification of the anthracene core influences energetics of both the isolated molecule and the crystal lattice. We use both density functional theory and dispersion-corrected Moller–Plesset perturbation theory computational methods to establish orbital energies, photodimerization reaction energies, and lattice energies for a set of substituted 9-anthracene carboxylic acid molecules. The calculations reveal that steric interactions play a dominant role in the ability to form photodimers and indicate an energetic threshold of 80–90 kJ per mole for the dimerization reaction. Examination of intermolecular bonding in a subset of fluorinated 9ACs revealed the absence of H⋯F intermolecular bond formation and energy differences that can explain observed trends in the dissociation kinetics and mechanical reset times. Fluorescence recovery after photobleaching experiments shows that the photodimer dissociation kinetics depend on the amount of initial photodimer, preventing a straightforward correlation between halogen atom substitution and dissociation rates using the Bell–Evans–Polanyi principle. The results clarify how molecular structure affects intermolecular interactions and photoreactivity in this family of molecular crystals, but the origin of the complex photodimer dissociation dynamics remains an open question.

Being a close analogue of amflutizole, methyl 4-amino-3-phenylisothiazole-5-carboxylate (C11H10N2O2S) was assumed to be capable of forming polymorphic structures. Noncentrosymmetric and centrosymmetric polymorphs have been obtained by crystallization from a series of more volatile solvents and from denser tetrachloromethane, respectively. Identical conformations of the molecule are found in both structures. The two polymorphs differ mainly in the intermolecular interactions formed by the amino group and in the type of stacking interactions between the π-systems. The most effective method for revealing packing motifs in structures with intermolecular interactions of different types (hydrogen bonding, stacking, dispersion, etc.) is to study the pairwise interaction energies using quantum chemical calculations. Molecules form a column as the primary basic structural motif due to stacking interactions in both polymorphic structures under study. The character of a column (straight or zigzag) is determined by the orientations of the stacked molecules (in a `head-to-head' or `head-to-tail' manner). Columns bound by intermolecular N—H...O and N—H...N hydrogen bonds form a double column as the main structural motif in the noncentrosymmetric structure. Double columns in the noncentrosymmetric structure and columns in the centrosymmetric structure interact strongly within the ab crystallographic plane, forming a layer as a secondary basic structural motif. The noncentrosymmetric structure has a lower density and a lower (by 0.59 kJ mol−1) lattice energy, calculated using periodic calculations, compared to the centrosymmetric structure.

Quasiracemates – materials consisting of pairs of near enantiomers – form crystalline motifs that mimic the inversion relationships observed for their racemic counterparts. Recent investigations from our group explored a family of chiral (N-benzoyl)methylbenzylamines to understand the structural boundary of cocrystallization. This investigation extends these earlier studies to include naphthylamide quasiracemates, where the molecular framework is ∼20% larger by volume than the previous diarylamides. A family of naphthylamides was prepared where the pendant functional group differs incrementally in size (i.e., H to C6H5) to give 55 possible unique pairs of racemic and quasiracemic combinations. Data collected from these materials using X-ray crystallography, thermal analysis methods and lattice energy calculations offer important insight into how a spatially larger naphthylamide molecular framework promotes greater structural variance of substituents during the pairwise assembly of quasienantiomers.

Cordierite ceramic is one kind of important electronic materials for radio frequency circuit. In this work, Mg2-x (Li0.5Ga0.5)xAl4Si5O18 (0 ≤ x ≤ 0.1) ceramics with pure cordierite phase, were successfully synthesized via the traditional solid state reaction method. The dependence of microwave dielectric properties on the crystal structure was analyzed in detail by the complex chemical bond theory (P–V-L theory) and classical dielectric polarizability theory. The dielectric constant (er) was mainly related to the density, bond ionicity and ionic polarizability of Mg2-x (Li0.5Ga0.5)xAl4Si5O18 ceramics. The quality factor (Q × f) was in relationship to the lattice energy, atomic packing fraction and centrosymmetry of [Si4Al2O18] hexagonal ring in cordierite crystal structure. The temperature coefficient of resonant frequency (τf) value was dominated by the bond energy and distortions of [MgO6] octahedron. The maximum values of Q × f = 50,560 GHz and er = 4.72 were obtained for undoped Mg2Al4Si5O18 and Mg1.98Li0.01Ga0.01Al4Si5O18, respectively.

Crystal structure prediction (CSP) calculations can reduce risk and improve efficiency during drug development. Traditionally CSP calculations use lattice energies computed through density function...

Single crystals of two polymorphic forms of 4′-methyl-2,4-dinitrodiphenylamine were obtained by crystallization and characterized by X-ray diffraction analysis. One of the forms is non-centrosymmetric (space group P21212), while the second is centrosymmetric (space group P¯1) and contains two crystallographically independent molecules in the asymmetric unit. In both forms, the same supramolecular synthon, a dimer linked by bonding N-H···O, O···O, and C-H···O interactions were found. Despite nearly the same connectivity of the bonding interactions, the conformation of the supramolecular synthon is different, including its unavoidably different symmetry in two polymorphs. The comparison of the crystal packing of the orthorhombic polymorph with that of the related 2,4-dinitrodiphenylamine (space group P21/n) shows the quasi-isostructurality of the fragments, infinite π-stacks joined by weak non-directional intermolecular interactions. However, the fragments are linked by the supramolecular synthons via either a two-fold axis or an inversion center, which lead to only the partial isostructurality of the crystals.

Two polymorphic forms of a conformationally flexible molecule, 5-[(Diphenylphosphoryl)methyl]-4-(prop-2-en-1-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione, were obtained by crystallization and characterized by X-ray diffraction analysis and differential scanning calorimetry. The relative stability of polymorphic forms was estimated with DFT calculations of crystal structures and isolated molecules. It turns out, that in the first more dense polymorph with higher cohesion energy and crystal lattice energy, the molecule adopts an energetically unfavorable conformation, and forms dimers with lower H-bond strength, as compared to the second polymorph. On the other hand, in the second polymorph, the molecule adopts almost the lowest-energy conformation and forms infinite chains via strong H-bonds. The first form that seems to be more thermodynamically stable at room temperature transforms into the second form via two endothermic phase transitions, the apparent irreversibility of the transition is due to high energy difference between the molecular conformations in crystals.

Four new solvates of the anti-HIV compound etravirine [systematic name: 4-({6-amino-5-bromo-2-[(4-cyanophenyl)amino]pyrimidin-4-yl}oxy)-3,5-dimethylbenzonitrile, C20H15BrN6O] with dimethyl sulfoxide (C2H6OS, two distinct monosolvates), 1,4-dioxane (C4H8O2, the 0.75-solvate) and N,N-dimethylacetamide (C4H9NO, the monosolvate), which exhibit conversion to the same anhydrous etravirine phase upon desolvation, and a stable etravirinium oxalate salt {6-amino-5-bromo-4-(4-cyano-2,6-dimethylphenoxy)-2-[(4-cyanophenyl)amino]pyrimidin-1-ium hemioxalate, C20H16BrN6O+·0.5C2O4 2−} were obtained. The crystal structures were solved by single-crystal X-ray diffraction and analyzed by powder X-ray diffraction, and the intermolecular interactions were explored by Hirshfeld surface analysis. Lattice energies were evaluated using the atom–atom force field Coulomb–London–Pauli (AA CLP) approximation, which distributes the total energy as four separate contributions: Coulombic, polarization, dispersion and repulsion. The formation of the solvates and the oxalate salt was further characterized by thermal analysis and IR spectroscopy.

Yttria-stabilized zirconia (YSZ), 15 wt.%Al2O3-doped YSZ (YSZ-15 wt.%Al2O3), and 35 wt.%Al2O3-doped YSZ (YSZ-35 wt.%Al2O3) coatings were prepared by atmospheric plasma spraying. Composition and microstructure of the coatings were characterized. Moreover, the effect of composition and microstructure on the thermal conductivities and thermal expansion coefficients (TECs) of the coatings was investigated. The YSZ-15 wt.%Al2O3 coatings possess much lower thermal conductivity compared to YSZ coating which is attributed to the smaller grains, more oxygen vacancies and the large atomic weight difference between Al and Zr. The mentioned factors improve the phonon scattering thereby reducing the thermal conductivity. The lower TECs of YSZ-15 wt.%Al2O3 coatings are attributed to the smaller lattice parameters due to the substitutional Al3+ doping at Zr4+ sites. The decrease in lattice parameter values increases the crystal lattice energy. And the TEC is inversely proportional to the lattice energy. Moreover, the TEC of the YSZ-35 wt.%Al2O3 coating is much lower than the YSZ coating, which is due to the precipitation of Al2O3 and the formation of amorphous phases. Compared to ZrO2 phase, the Al2O3 phase possesses lower TECs values. The amorphous phase can account for larger expansion tolerance compared to the corresponding crystalline phase due to its loose atomic arrangement.

Thalassemia is a genetic blood disorder requiring life-long blood transfusions. This process often results in iron overload and can be treated by an iron-chelating agent, like deferiprone (3-hydroxy-1,2-dimethylpyridin-4-one), C7H9NO2, in an oral formulation. The first crystal structure of deferiprone, (Ia), was reported in 1988 [Nelson et al. (1988). Can. J. Chem. 66, 123–131]. In the present study, two novel polymorphic forms, (Ib) and (Ic), of deferiprone were identified concomitantly with polymorph (Ia) during the crystallization experiments. Polymorph (Ia) was redetermined at low temperature for comparison of the structural features and lattice energy values with polymorphs (Ib) and (Ic). Polymorph (Ia) crystallized in the orthorhombic space group Pbca, whereas both polymorphs (Ib) and (Ic) crystallized in the monoclinic space group P21/c. The asymmetric units of (Ia) and (Ib) contain one deferiprone molecule, while polymorph (Ic) has three crystallographically independent molecules (A, B and C). All three polymorphs have similar hydrogen-bonding features, such as an R 2 2(10) dimer formed by O—H...O hydrogen bonds, an R 4 3(20) tetramer formed by C—H...O hydrogen bonds and π–π interactions, but the polymorphs differ in their molecular arrangements in the solid state and are classified as packing polymorphs. O—H...O and C—H...O hydrogen bonds lead to the formation of two-dimensional hydrogen-bonded parallel sheets which are interlinked by π–π stacking interactions. In the three-dimensional crystal packing, the deferiprone molecules were aggregated as corrugated sheets in polymorphs (Ia) and (Ic), whereas in polymorph (Ib), they were aggregated as a square-grid network. The characteristic crystalline peaks of polymorphs (Ia), (Ib) and (Ic) were established through powder X-ray diffraction analysis. The Rietveld analysis was also performed to estimate the contribution of the polymorphs to the bulk material.

A set of 377 crystal structures extracted from the Cambridge Structural Database and matched to the experimental sublimation enthalpies of the corresponding materials is used to calibrate a new intermolecular potential field for organic compounds. The scheme includes usual R−6–R−12 Lennard-Jones dispersion–repulsion terms, with parameters for C, H, N, O, S and the halogens, fully transferable and unique for each atomic species without distinction among the hybridization states of carbon, or among valence states like carbonyl or ether oxygen or aza, nitro or nitrile nitrogen. This great economy in the number of parameters is countered by the need for using accurate coulombic terms over atomic point charges derived for each molecule from the fitting of the electrostatic potential (ESP method) of an ab initio MP2/6-31G** wavefunction. The potential scheme so derived, called Mi-LJC (Milano Lennard-Jones Coulomb), is able to reproduce the 377 sublimation enthalpies by the calculated lattice energies with an average percent deviation of 5% and a rmsd of 6.7 kJ mol−1. The potential scheme is also tested and proved applicable for the Monte Carlo simulation of some organic liquids, as well as for the molecular dynamic simulation of liquids and crystals.

Experimental and theoretical electron density distributions and the nature of intermolecular interactions of bicalutamide in its monoclinic polymorph and in androgen receptor complexes are reported., High-resolution single-crystal X-ray measurements of the monoclinic polymorph of bicalutamide and the aspherical atom databank approach have served as a basis for a reconstruction of the charge density distribution of the drug and its androgen receptor (AR) and albumin complexes. The contributions of various types of intermolecular interactions to the total crystal energy or ligand:AR energy were estimated. The cyan and amide groups secured the ligand placement in the albumin (Lys-137) and the AR binding pocket (Leu-704, Asn-705, Arg-752), and also determined the packing of the small-molecule crystals. The total electrostatic interaction energy on average was −230 kJ mol−1, comparable with the electrostatic lattice energy of the monoclinic bicalutamide polymorph. This is the result of similar distributions of electropositive and electronegative regions on the experimental and theoretical molecular electrostatic potential maps despite differences in molecular conformations. In general, bicalutamide interacted with the studied proteins with similar electrostatic interaction energies and adjusted its conformation and electrostatic potential to fit the binding pocket in such a way as to enhance the interactions, e.g. hydrogen bonds and π⋯π stacking.

In the equilibrium state, carbon vacancies in the zirconium carbide lattice are ordered (spaced by maximum distances from each other) to minimize the lattice energy, which makes the lattice structure layered, with vacancies located in each second layer of the lattice. The outcrop of this weakened layer onto the crystal surface is succeeded by its decomposition after achieving a certain temperature, with the formation of a liquid phase of the corresponding composition. This is the reason for the stepwise form of the left boundary of the lattice homogeneity region, which does not contradict the known experimental and calculated data. It is suggested that a zirconium carbide melt can be molecular in a certain stoichiometry region and form one or more immiscibility gaps.

The solid state assembly of two cyclic hexapeptoids decorated respectively with five and six carbon N-alkyl side chains is analyzed by single crystal X-ray diffraction, intermolecular energies and lattice energy calculations. Thermal analysis and variable temperature X-ray powder diffraction were also carried out to analyze their thermal behaviour. The crystal structures of the two compounds feature architectural similarities, but also small relevant differences due to side chains-to-side chains interactions, which can explain the observed differences in the thermal properties. The compound with N-pentyl side chains exhibits a phase transition upon cooling down from room temperature to 100 K, while that with N-hexyl side chains features no phase transformation on cooling, instead a phase transformation occurs at 335 K upon heating.

Polymorphism represents an expanding area of crystal engineering and an opportunity for discovery of materials with interesting properties, thus giving new perspectives for “old”, well-known compounds known by chemists for decades. In this work, we revisit 2-chloro-4-nitroaniline (2Cl4na) for which the crystal structure was first determined as early as 1965. Our failed trials to reproduce the original orthorhombic phase of 2Cl4na led to the determination of its new triclinic polymorph. Synthetic screening indicated that 2Cl4na can be obtained from several solvent mixtures as well as by slow cooling of the melted sample. This polymorph crystallizes in the non-centrosymmetric space group P1 with a = 3.7755(2) A, b = 13.5798(7) A, c = 28.554(1) A, α = 89.503(4)°, β = 88.612(4)° and γ = 86.402(4)° lattice parameters and Z = 8. This high number of crystallographically equivalent molecules in the independent part of the unit cell resulted in an unusual supramolecular arrangement of this compound. Energy vector diagrams indicate that the structure of the previously known orthorhombic polymorph is columnar, whereas the triclinic one is quasi-isotropic. Calculations of lattice energies by an ab initio method with periodic boundary conditions showed that the triclinic polymorph is more stable by 0.89 kcal mol−1 in comparison to the orthorhombic one. The cooperative character of weak hydrogen bonds and stacking interactions was suggested as a key governing factor in the crystal growth of needle-like crystals. With the use of the Kurtz–Perry test we also demonstrate that this new polymorphic form of 2Cl4na produces second harmonic generation (SHG) that is 2 times higher than that obtained from potassium dihydrogen phosphate (KDP) upon irradiation with an 800 nm laser beam. Alongside the strong SHG, greenish-yellow two-photon excited fluorescence is also observed.

Cocrystallization technology is an effective method for improving crystal properties. Ammonium dinitramide (ADN) is an important component of propellants. However, the high hygroscopicity property of ADN limits its applications. In order to solve this problem, nine energetic co-formers containing 2,4,5,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), benzotrifuroxan (BTF), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), 2,4,6-trinitrotoluene (TNT), butane-1,2,3,4-tetrayl tetranitrate (ETN), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitro-N-methylaniline (MATNB), and 1,3,3- trinitroazetidine (TNAZ) were selected to predict the hygroscopicity of co-crystals with the molar ratio of ADN to co-former as 1 : 1. A novel computational method has been put forward to select co-formers efficiently for designing energetic co-crystals with a low water sorption capacity. Based on the molecular electrostatic potential calculations, the intermolecular binding sites in the co-formers of co-crystal were found. By the lattice energy minimization methodology, the possible crystal structures were constructed, and the density and H-bond energy of possible energetic co-crystals were predicted. The co-crystal screening method was used to calculate pairwise interactions and select promising co-crystal formers for the experimental screening. This method can be used to predict the co-crystal hygroscopicity, which thus may speed up the progress of developing novel energetic co-crystal materials.

Structure–property correlation is an important aspect in crystal engineering which has direct applications in the development of pharmaceutical solid dosage forms. In this manuscript, we present a combined structural, thermal and computational study of seven new cocrystals and cocrystal solvates of an antipsychotic drug, olanzapine, with three coformers (hydroquinone, resorcinol and catechol) and attempt to understand the effect of solid-state molecular packing on the thermal properties (desolvation and melting behaviour). The cocrystals were designed by utilizing the robust hydrogen-bonded synthons between the drug and coformers, while the cocrystal solvates were obtained by the isostructural replacement of toluene in a previously reported multicomponent structure by benzene, xylene and ethyl benzene. The positional variations of hydroxyl groups in coformer molecules had a remarkable influence on the crystal packing of cocrystals. The olanzapine–hydroquinone (OLZ–HQ) combination in 1 : 1 stoichiometry crystallized as cocrystal solvates that was attributed to the persistent formation of rectangular hydrogen-bonded grid networks with inherent hydrophobic cavities for aromatic guest molecule inclusion. In contrast, the olanzapine–resorcinol (OLZ–RES) and olanzapine–catechol (OLZ–CAT) combinations in 1 : 1 stoichiometry resulted in non-solvated cocrystals and can be classified as pharmaceutical cocrystals. The desolvation patterns of cocrystal solvates were explained based on the structural similarities and dissimilarities, host–guest interactions, void types (closed vs. open), void size (narrow and wide), packing coefficients and boiling points of the guest molecules. Solid-state DFT calculations were performed to assess the desolvation energies, stabilization energies of desolvated systems and lattice energies of all cocrystals and cocrystal solvate systems and the results were correlated with the experimental observations. The solvent molecules play an important role in the structure stabilization, rendering the crystal lattice of the OLZ–HQ structure energetically feasible and compensating for the loss of packing density rather than simply occupying the void space in the crystal structure. The large melting point differences and thermal stabilities of two anhydrous cocrystals (M.P. of OLZ–RES is 196 °C and M.P. of OLZ–CAT is 135 °C) were also explained on the basis of packing coefficients and lattice energy calculations.

There are the chains of transition-metal cations alternating with the anions of oxygen in ternary transition-metal oxides. When a p-orbital of the oxygen connects the half-filled and empty d-orbitals of adjacent transition-metal cations, double-exchange ferromagnetism takes place. Although double exchange has been well explored, the nature of novel criticality, induced by it, is yet not uncovered. We explored the magnetic-field scaling in the heat capacity of a Sm0.55Sr0.45MnO3 manganite, one of the best ternary transition-metal oxides as it is completely ferromagnetic, and found novel criticality - unordinary critical exponents which are the consequence of coherence of Coulomb lattice distortion and ferromagnetism. The coherence is caused by the trinity of the mass, the charge and the spin of an electron. When the d and p orbitals overlaps, it quickly walks from one site to the another due its lightest mass. And due to its electric charge, it equalizes the valences of the transition-metal cations in the chains and so diminishes the Coulomb lattice distortion. At last, its spin forces magnetic moments of transition-metal cations to ferromagnetically arrange. The disappearance of Coulomb distortions widens the overlap and lowers the elastic lattice energy, so that not only the spin of an electron, but also its electric charge strengthens ferromagnetism. That nonlinear effect strengthens the critical behaviour and critical exponents come off any known universality classes. Thus, the symbiotic coherence of annihilating Coulomb distortions and arising ferromagnetism is a reason of the novel criticality.

The consistency and variability as well as self-assembly evolution mechanism of cresol–piperazine cocrystals are investigated by experiments and molecular simulation., The disposition of functional groups can induce variations in the nature and type of interactions and hence affect the molecular recognition and self-assembly mechanism in cocrystals. To better understand the formation of cocrystals on a molecular level, the effects of disposition of functional groups on the formation of cocrystals were systematically and comprehensively investigated using cresol isomers (o-, m-, p-cresol) as model compounds. Consistency and variability in these cocrystals containing positional isomers were found and analyzed. The structures, molecular recognition and self-assembly mechanism of supramolecular synthons in solution and in their corresponding cocrystals were verified by a combined experimental and theoretical calculation approach. It was found that the heterosynthons (heterotrimer or heterodimer) combined with O—H⋯N hydrogen bonding played a significant role. Hirshfeld surface analysis and computed interaction energy values were used to determine the hierarchical ordering of the weak interactions. The quantitative analyses of charge transfers and molecular electrostatic potential were also applied to reveal and verify the reasons for consistency and variability. Finally, the molecular recognition, self-assembly and evolution process of the supramolecular synthons in solution were investigated. The results confirm that the supramolecular synthon structures formed initially in solution would be carried over to the final cocrystals, and the supramolecular synthon structures are the precursors of cocrystals and the information memory of the cocrystallization process, which is evidence for classical nucleation theory.

The phase transformation of chalcopyrite and the effect of its phase status on bacterial leaching were studied. Under the protection of high-purity argon, different temperatures (203, 382 and 552 °C) were applied to natural chalcopyrite to complete the phase change. In addition, the chalcopyrite was bioleached before and after the phase change. The results show that the chalcopyrite heated at 203 and 382 °C remained in the α phase, whereas the chalcopyrite changed from α to β phase at 552 °C. The leaching rates of chalcopyrite after the phase transitions at 203, 382 and 552 °C were 32.9%, 40.5% and 60.95%, respectively. Further, the crystal lattice parameters of chalcopyrite increased and lattice energy decreased, which were the fundamental reasons for the significant increase in leaching rate. Electrochemical experiments demonstrated that with increasing annealing temperature, the polarization resistance decreased and corrosion current density increased. The higher the oxidation rate was, the higher the leaching rate was.

MgZrNb2−x(Sn1/2W1/2)xO8 (0 ≤ x ≤ 0.15) dielectric ceramics were synthesized through solid state reaction route. SnO2, WO3 and Nb2O5 were pre-calcined to promote the substitution element to fully enter the Nb-site when reacting with MgO and ZrO2. The formation of solid solutions with monoclinic wolframite structure were confirmed. Rietveld refinement and P–V–L theory were used as intrinsic factors of analyzing the changes in microwave dielectric properties. With the increase of (Sn1/2W1/2)5+ substitution amount, er of highly densified MgZrNb2−x(Sn1/2W1/2)xO8 ceramic decreased slowly, which was mainly ascribed to low bond iconicity. The optimal substitution of isovalent composite ions enhances the total lattice energy, leading to an increase in Q × f value. The increase of τf was closely correlated with the decrease of the total bond energy. When x = 0.06, the optimal dielectric properties, er= 24.61, Q × f = 93346.3 GHz, τf= − 48.46 ppm/°C, were successfully obtained for the MgZrNb2−x(Sn1/2W1/2)xO8 specimens sintered at 1300 °C.

A database of 1655 critically evaluated sublimation enthalpies of organic compounds is presented. Experimental techniques are briefly reviewed. The consistency of experimental measurements is criti...

The synthesis and detailed description of the crystal structure and energetic features of the 1:1 cocrystal of carbamazepine (5H-dibenzo[b,f]azepine-5-carboxamide, CBZ) with 3,5-dinitrobenzoic acid (35DNBA), i.e. C15H12N2O·C7H4N2O6, are reported. The CBZ and 35DNBA molecules are packed in alternately arranged layers. Two characteristic R 2 2(8) and R 2 2(16) hydrogen-bond ring motifs have been found. The supramolecular architecture, besides the network of hydrogen bonds, is also stabilized by numerous C—H...π, C=O...π, N—O...π, N—O...C and C=O...N weak intermolecular contacts involving neighbouring molecules in the crystal network. Identified interactions have been discussed in detail on the basis of a structural and energetic analysis. The latter approach, performed using the Pixel and CrystalExplorer programs, yielded additional information about the lattice energy and energetic landscape of the respective interactions in the crystal of CBZ·3DNBA with the evaluation of electrostatic, polarization, repulsion and dispersion terms.

Here we investigate analytical models to understand magnetic and magnetocaloric properties of Mn5Ge2.9Ag0.1 compound prepared by arc-melting method. The Mn5Ge2.9Ag0.1 alloy, undergoing a second-order transition, shows a maximum magnetic entropy change of about 6.86 J/kgK and the relative cooling power (RCP) value of 386 J/kg at 298 K under a field change of 5T. Based on a phenomenological model, the magnetocaloric properties obtained from temperature-dependent magnetization data are in good agreement with the experimental results. To give a better understanding of magnetic transition and the effective magnetic entropy change, we quantify the coupling of lattice energy and electronic energy contribution to the effective magnetic entropy change from a Landau theory plus Bean-Rodbell model. Interestingly, the coupling of lattice energy and electronic energy presents a positive value of up to 4.5% of the effective magnetic entropy change, producing a deleterious impact on the effective magnetic entropy change. The results suggest that the Mn5Ge2.9Ag0.1 system could be a very attractive material for room-temperature magnetic refrigeration applications.

Atomistic simulations based on lattice energy minimization are used to investigate trivalent and divalent Europium dopant ions in the structure of KMPO4 (M = Ba and Sr). Interatomic potentials are developed, and the structural properties calculated in this way show good agreement with experimental values. These calculations suggest that Eu3+ and Eu2+ ions are the most energetically provable to be incorporated at divalent (M = Ba and Sr) host sites. It is also predicted that the Eu divalent dopant is charge-compensated by KMʼ anti-site defects. Four reduction-doping process schemes (open atmosphere, CO, N2 and H2 reducing atmosphere) are investigated here, and it is observed that a CO reducing atmosphere is the most effective agent for Eu reduction. The results showed that the preferred host site, charge compensation and schemes for the reduction-doping process for Eu doping ions play important roles in an understanding of the luminescent properties of KMPO4 (M = Ba and Sr) phosphates.

In this work, the thermal stability of CuCl2, CoCl2, MnCl2, and their corresponding hydrates was studied by combining with calorimetry and lattice energy calculation. The dissolution enthalpies of both anhydrates and hydrates in water with different molalities at 298.15 K were measured to calculate the standard molar enthalpies of formation. The hydration enthalpies and the lattice energies were calculated to disclose the stabilities of the compounds, indicating that the MnCl2·4H2O has the highest stability among the three hydrates. Meanwhile, the detailed thermal decomposition behaviors were evaluated with differential scanning calorimetry and thermogravimetric analysis. For CuCl2·2H2O, the crystal water is lost by one step directly with the temperature ranges from 350 to 410 K. The decomposition process contains four steps for CoCl2·6H2O and obtains its monohydrate in the temperature range from 320 to 479 K. For MnCl2·4H2O, two thermal decomposition steps occur from 325 to 500 K, while two consecutive peaks with no clear boundary indicate that the complex reactions appear.

Strontium hydroxyapatite (SrHAp) is not only used as drug carrier material for bone disease treatment, but also has application prospect in bone tissue engineering. But SrHAp is prepared with by-products strontium hydrogen phosphate (SrHP) and strontium phosphate (TSrP), which requires accurate process optimizations and adjustments to circumvent the undesirable morphology products. The integral hexagonal prism crystals of SrHAp were successfully synthesized by urea hydrolysis at ambient pressure and without any strong acids and bases. Similarly, variable by-products are classified and investigated for their effects on crystallization process of strontium hydroxyapatite via monitoring the urea hydrolysis time-dependent products. The crystallization process of SrHAp can be divided into four stages based on the crystallographic results for the samples acquired by XRD and SEM studies during the entire synthesis processes. In the first stage, SrHP is formed (0–0.17 h); secondly, SrHP is converted into SrHAp (0.17–4 h); TSrP is obtained (4–8 h) at the third stage; and at last, TSrP is transformed into SrHAp (8–24 h), especially the amount of SrHAp obtained at 24 h was the sum of the second and fourth stages. Simultaneously, the growth mechanism of SrHAp crystals was proposed, considered of the formation energy of Gibbs-Thomson crystal plane and Born-Lande lattice energy. By calculating the interfacial energy γ(h k l) of different crystal planes, the γ(1 0 0) of hexagonal prism plane family m{1 0 0} is 1.3 × 10−5U0, the γ(0 0 1) of parallel double-plane family c{0 0 1} is 7.5 × 10−6U0, the normal growth rate of Ic{0 0 1} ≫ Im{1 0 0}. Accordingly, the growth mechanism for the preferential c axis growth maintaining the hexagonal prism shape is derived.

The control of the crystal form is a central issue in the pharmaceutical industry. The identification of putative polymorphs through Crystal Structure Prediction (CSP) methods is based on lattice energy calculations, which are known to significantly over-predict the number of plausible crystal structures. A valuable tool to reduce overprediction is to employ physics-based, dynamic simulations to coalesce lattice energy minima separated by small barriers into a smaller number of more stable geometries once thermal effects are introduced. Molecular dynamics simulations and enhanced sampling methods can be employed in this context to simulate crystal structures at finite temperature and pressure. Here we demonstrate the applicability of approaches based on molecular dynamics to systematically process realistic CSP datasets containing several hundreds of crystal structures. The system investigated is ibuprofen, a conformationally flexible active pharmaceutical ingredient that crystallises both in enantiopure forms and as a racemic mixture. By introducing a hierarchical approach in the analysis of finite-temperature supercell configurations, we can post-process a dataset of 555 crystal structures, identifying 65% of the initial structures as labile, while maintaining all the experimentally known crystal structures in the final, reduced set. Moreover, the extensive nature of the initial dataset allows one to gain quantitative insight into the persistence and the propensity to transform of crystal structures containing common hydrogen-bonded intermolecular interaction motifs.

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of isolated molecules modeled by DFT calculations. In a solvent with relatively small molecules (ethanol), IVM forms monoclinic crystal structure (space group I2), which contains two types of voids. When crystallized from solvents with larger molecules, like -valerolactone (GVL) and methyl tert-butyl ether (MTBE), IVM forms orthorhombic crystal structure (space group P212121). Calculations of the lattice energy indicate that interactions between IVM and solvents play a minor role, the main contribution to energy is made by the interactions between the molecules of IVM itself, which form a framework in the crystal structure. Interactions between IVM and molecules of solvents were evaluated using Hirshfeld surface analysis. Thermal analysis of the new pseudopolymorphs of IVM was performed by differential scanning calorimetry and thermogravimetric analysis.

This work is aim to understand the composition of chemical bonds and explore the mechanism to form different kinds of morphology of TMD nanocluster. We have developed a universal theory and methodology which can well predict the effective charge of a given materials from variant dimensions. The methodology has to be agile which can be extended to all the materials of all the dimensions, including 3D bulks, quasi 2D layer structures and nanoclusters. for the low dimensional materials, the quantum size effect, layer dependent effect and stacking dependent are all typical tasks to verify the robustness of the new theory extended in the low dimensions. The theory also used to understand the materials' properties in both the static property, like geometry shape, edge stability in nanoclusters, and dynamic property, like growth favorite sites in the nanoclusters. Doctor of Philosophy (IGS)

The dipharmacophore compound 3-cyclopropyl-5-(3-methyl-[1,2,4]triazolo[4,3-a]pyridin-7-yl)-1,2,4-oxadiazole, C12H11N5O, was studied on the assumption of its potential biological activity. Two polymorphic forms differ in both their molecular and crystal structures. The monoclinic polymorphic form was crystallized from more volatile solvents and contains a conformer with a higher relative energy. The basic molecule forms an abundance of interactions with relatively close energies. The orthorhombic polymorph was crystallized very slowly from isoamyl alcohol and contains a conformer with a much lower energy. The basic molecule forms two strong interactions and a large number of weak interactions. Stacking interactions of the `head-to-head' type in the monoclinic structure and of the `head-to-tail' type in the orthorhombic structure proved to be the strongest and form stacked columns in the two polymorphs. The main structural motif of the monoclinic structure is a double column where two stacked columns interact through weak C—H...N hydrogen bonds and dispersive interactions. In the orthorhombic structure, a single stacked column is the main structural motif. Periodic calculations confirmed that the orthorhombic structure obtained by slow evaporation has a lower lattice energy (0.97 kcal mol−1) compared to the monoclinic structure.

Systematic research on the response of crystal materials to the deposition of irradiation energy to electrons and atomic nuclei has attracted considerable attention since it is fundamental to understanding the behavior of various materials in natural and manmade radiation environments. This work examines and compares track formation in LiTaO3 induced by separate and combined effects of electronic excitation and nuclear collision. Under 0.71&ndash, 6.17 MeV/u ion irradiation with electronic energy loss ranging from 6.0 to 13.8 keV/nm, the track damage morphologies evolve from discontinuous to continuous cylindrical zone. Based on the irradiation energy deposited via electronic energy loss, the subsequently induced energy exchange and temperature evolution processes in electron and lattice subsystems are calculated through the inelastic thermal spike model, demonstrating the formation of track damage and relevant thresholds of lattice energy and temperature. Combined with a disorder accumulation model, the damage accumulation in LiTaO3 produced by nuclear energy loss is also experimentally determined. The damage characterizations and inelastic thermal spike calculations further demonstrate that compared to damage-free LiTaO3, nuclear-collision-damaged LiTaO3 presents a more intense thermal spike response to electronic energy loss owing to the decrease in thermal conductivity and increase in electron&ndash, phonon coupling, which further enhance track damage.

Crystal structure prediction methods are prone to overestimate the number of potential polymorphs of organic molecules. In this work, we aim to reduce the overprediction by systematically applying molecular dynamics simulations and biased sampling methods to cluster subsets of structures that can easily interconvert at finite temperature and pressure. Following this approach, we rationally reduce the number of predicted putative polymorphs in CSP-generated crystal energy landscapes. This uses an unsupervised clustering approach to analyze independent finite-temperature molecular dynamics trajectories and hence identify a representative structure of each cluster of distinct lattice energy minima that are effectively equivalent at finite temperature and pressure. Biased simulations are used to reduce the impact of limited sampling time and to estimate the work associated with polymorphic transformations. We demonstrate the proposed systematic approach by studying the polymorphs of urea and succinic acid, reducing an initial set of over 100 energetically plausible CSP structures to 12 and 27 respectively, including the experimentally known polymorphs. The simulations also indicate the types of disorder and stacking errors that may occur in real structures.

Neodyme spherical magnets are inexpensive objects that demonstrate how dipolar particles self-assemble into various structures ranging from 1D chains to 3D crystals. The dipole-dipole interactions confer the stability to these particular architectures. In the present paper, we explore ordered structures only, and we evidence that hybrid magnetocrystals, alternating hexagonal planes of antiparallel dipoles, have the lowest magnetic energy. This cohesion is the magnetic counterpart of the Madelung lattice energy found for ionic solids.

The dipharmacophore compound 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole, C10H11N5O, was studied on the assumption of its potential biological activity. Two concomitant polymorphs were obtained on crystallization from isopropanol solution and these were thoroughly studied. Identical conformations of the molecules are found in both structures despite the low difference in energy between the four possible conformers. The two polymorphs differ crucially with respect to their crystal structures. A centrosymmetric dimer formed due to both stacking interactions of the `head-to-tail' type and N—H...N(π) hydrogen bonds is the building unit in the triclinic structure. The dimeric building units form an isotropic packing. In the orthorhombic polymorphic structure, the molecules form stacking interactions of the `head-to-head' type, which results in their organization in a column as the primary basic structural motif. The formation of N—H...N(lone pair) hydrogen bonds between two neighbouring columns allows the formation of a double column as the main structural motif. The correct packing motifs in the two polymorphs could not be identified without calculations of the pairwise interaction energies. The triclinic structure has a higher density and a lower (by 0.60 kcal mol−1) lattice energy according to periodic calculations compared to the orthorhombic structure. This allows us to presume that the triclinic form of 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole is the more stable.

Ionic compounds wherein lanthanide cations are arrayed alongside anions adopt a wide range of crystal structures as a result of the variation of ionic radii and electronic configurations across the lanthanide series. Owing to the constricted nature of 4f orbitals, local coordination environments and structural preferences in such compounds are primarily dictated by electrostatic interactions and steric considerations with the primary driving force being the minimization of the crystal lattice energy. In this review, we examine a broad class of dianionic rare-earth compounds, lanthanide oxyhalides that present a multidimensional design space for tuning of functional properties by dint of the possibilities for extensive alloying on cationic and anionic sublattices; the considerable span of ionic radii and hardness across the lanthanide series and down the halide group, respectively; a large tolerance window for point defects such as oxide and halide vacancies; as well as multiple accessible polymorphs. In addition to their structural versatility, control over functional properties is accessible based on alteration of microstructure and surface chemistry. Synthetic strategies for accessing atomistic, nanoscale, and mesoscale control are discussed using illustrative examples placing particular emphasis on non-hydrolytic sol—gel processes that provide access to well-defined solid-solution nanocrystals. The reactivity and post-synthetic modification of these compounds is further delineated. Methods for defining color centers within these compounds, cooperativity of the optical response of the color centers with the host lattice (determined by overlap integrals specific to each structure type and the polarization and ligand field effects of different halide ions) and adjacent color centers (reliant on energy transfer schema), and their practical application in phosphors are further detailed. Mechanisms facilitating down- and up-conversion of energy absorbed from incident electromagnetic radiation or high-energy particles are delineated with particular emphasis on X-ray and electron-beam excitation. The accessible energy conversion mechanisms, efficacious radiative recombination channels, and opportunities for systematically tuning color through compositional modulation have led to the emergence of these materials as potential candidates for phosphors. These materials have potential applications in solid-state lighting, radiation detection, and as the active elements of imaging devices. The tolerance towards large concentrations of anion vacancies and the facile diffusivity of anions in these compounds further underpins the function of lanthanide oxyhalides as ion conductors, gas sensors, and heterogeneous catalysts. Increasing interest has focused on utilization of well-defined color centers for quantum information science and multiplexed sensing in biological systems. Such applications require additional control of the positioning of dopant atoms and understanding of their interactions with the host lattice and other dopant atoms.

Magnesium melilite (Ca2MgSi2O7) ceramic with tetragonal crystal structure was prepared through the conventional solid-state method. Crystal structure and complex chemical bond theory were used to analyze the microwave properties of Ca2MgSi2O7 ceramics and the correlations between the bond ionicity, lattice energy, bond energy and relative dielectric constant (er), quality factor (Q × f0), temperature coefficient of resonant frequency (τf) were discussed in depth. Optimum microwave dielectric properties were obtained when sintered at 1300°C for 4 h: er= 9.86, the dielectric loss (tanδ) was 1.24 × 10−4 (at 1 MHz), Q × f0= 8016 GHz (resonant frequency f0 = 7.90 GHz), τf= − 42 ppm/°C.

We demonstrate, for four different systems of pharmaceutical relevance, that ball mill grinding leads to different polymorphic transformations dependending on the milling conditions. In all four cases, the commercial polymorph converts to a different polymorph upon ball-mill neat grinding (NG). This transformation can be reversed by grinding the so obtained polymorph in the presence of small amounts of solvent (LAG), leading back to the commercial polymorph. Scherrer particle size determinations reveal that NG conditions almost always lead to smaller particle sizes in the nanometer length scales. Computational studies confirm that polymorphs obtained by the specific ball mill LAG conditions reported correspond to the the lowest lattice energy forms. Our study further confirms our earlier conclusions that, at the nanoscale, polymorphs with higher lattice energies can become the thermodynamically stable forms if their surfaces are more stable than those of the polymorphs obtained by LAG. We found, however, one exception to this trend in D-sorbitol. We observe that polymorphs with smoother surfaces (low roughness) are usually the ones observed by NG. This observation points to a link between surface roughness and surface stability.

The ability to perform large-scale crystal structure predictions (CSPs) has significantly advanced the synthesis of functional molecular solids by design. In our recent work [J. Yang, S. De, J. E. Campbell, S. Li, M. Ceriotti and G. M. Day, Chem. Mater., 2018, 30, 4361], we demonstrated our latest developments in organic CSPs by screening a set of 28 pyrrole azaphenacene isomers which led to one new molecule with higher thermodynamic stability and carrier mobilities in its crystalline form, compared to the one reported experimentally. Hereby, using the lattice energy landscapes of pyrrole azaphenacenes as examples, we applied machine-learning techniques to statistically reveal, in more detail, how molecular symmetry and Z′ values translate to the crystal packing landscapes, which in turn affect the coverage of landscapes through quasi-random crystal structure samplings. A recurring theme in crystal engineering is to identify the probabilities of targeting isostructures to a specific reference crystal upon chemical functionalisations. For this, we propose here a global similarity index in conjunction with an energy–density–isostructurality (EDI) map to analyse the lattice energy landscapes of halogen substituted pyrrole azaphenacenes. A continuous effort in the field is to accelerate CSPs for sampling a much wider chemical space for high-throughput material screenings, and we propose a potential solution to this challenge drawn upon this study. Our work will hopefully stimulate the crystal engineering community in adapting a more statistically-oriented approach in understanding the crystal packing of organic molecules in the age of digitisation.

Cocrystal formation of 4-aminobenzoic acid (PABA) has been screened with a variety of pyrimidine, pyridine and benzamide derivatives to understand how hydrogen bond donor/acceptor ratios and the position of a substituting group of the coformers affect cocrystallization. Four new cocrystals with 6-methyluracil (6-MeUr), barbituric acid (BarbAc), 2-hydroxybenzamide (2-OHBZA), 4-hydroxybenzamide (4-OHBZA) and one salt with emoxypine (EMX) have been successfully obtained from solvent evaporation experiments, and their crystal structures have been determined. Analysis of the hydrogen bonding motifs has shown that all the two-component crystals, except for the [PABA + 4-OHBZA] cocrystal, feature acid⋯amide or acid⋯pyridine heterosynthons between the components. The melting temperatures and crystal lattice energy values of the novel PABA multi-component crystals have been described. The temperature dependences of the 6-MeUr and EMX saturation vapour pressure have been studied, and the sublimation thermodynamic functions have been calculated. The thermodynamic functions of cocrystal formation based on PABA have been calculated and analyzed by the diagram method.

The effects of high pressure and low temperature have been explored on the ‘orange-plate’ (OP) form of the highly-polymorphic 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile molecular crystal structures. Neutron powder and single-crystal diffraction measured up to 9.3 GPa and 40 K, respectively, show that the crystal structure is robust, retaining P21/n symmetry over the pressure and temperature range studied, even though it is revealed to be quite soft, having a bulk modulus of 4.3(3) GPa. Intermolecular and lattice energies become progressively less favourable with pressure, relative to the thermodynamically-stable ‘yellow’ (Y, P21/n) form, showing that the kinetic barriers to transformation, stabilising the material, persist from ambient to extreme conditions.

Dapsone (DDS) shows a rich solid form landscape, comprising five anhydrates, one hydrate and 15 solvates. The four isostructural DDS hemisolvates, with dichloromethane, acetonitrile, nitromethane and dimethyl sulfoxide as guest molecules, obtained by cooling crystallisation, slurry or solvent vapour diffusion experiments were investigated in this study. Experimental (thermal analysis and X-ray diffraction) and computational studies (lattice, intermolecular and stability energy calculations) were undertaken to rationalise and understand (hemi)solvate formation, stability and phase transitions occurring during the desolvation of the solvates. It was found that DDS⋯solvent interactions and the shape/size of the solvent molecules are critical for solvate formation. Careful control of the experimental crystallisation and storage conditions were required for identifying and characterising solvates that are unstable at ambient conditions. The solvent molecules of the hemisolvates are located at isolated-sites and form strong hydrogen bonds and/or interactions involving dispersion forces. The isostructurality of the four hemisolvates was confirmed by single crystal X-ray diffraction determinations and modelling, i.e. solvent exchange calculations. Furthermore, the formation of either the hemi- or monosolvate stoichiometry was rationalised on the basis of lattice energy calculations.

An elegant statistical mechanics approach has been exploited in combination with accurate quantum chemical calculations to justify the disorder in two previously reported racemic solids. Generated canonical ensembles and performed lattice energy calculations show that the disorder in the studied systems of small organic enantiomer molecules can be modelled with great accuracy. Ensemble averages fully correspond to the disordered structure models repeatedly obtained in X-ray diffraction studies. The present work not only demonstrates that disorder and its extent in molecular crystals can be theoretically calculated, but also explains from a thermodynamic point of view the origins of the rarely encountered phenomenon of enantiomer solid solutions. Such phases are promising in materials science as their properties can be finely tuned depending on the composition. The lack of complete enantiomer discrimination in the studied examples is evident and it is related to the absence of any donor–acceptor groups providing highly directional interactions, as well as to conformational flexibility in one case and a specific inner symmetry of the molecule in the other one.

Molecular crystal engineering seeks to tune the material properties by controlling the crystal packing. However, the range of achievable properties is constrained by the limited energy range of polymorphs which can be crystallized. Here, computational modeling highlights that a solid-state crystal-to-crystal chemical reaction in 9-tert-butyl anthracene ester (9TBAE) nanorods [Al-Kaysi et al., J. Am. Chem. Soc., 2006, 128, 15938] imparts “synthetic memory” into the crystal structure that allows reproducible formation of a highly metastable, yet long-lived polymorph. Specifically, whereas the vast majority of known polymorphs exhibit lattice energy differences below 10 kJ mol−1, the conformational polymorph formed via solid state reaction chemistry lies 14 kJ mol−1 higher in energy than the form grown from solution, according to calculations that combine a dispersion-corrected second-order Moller–Plesset perturbation theory (MP2D) treatment of the monomer and photodimer with a density functional theory treatment (B86bPBE-XDM) of the intermolecular interactions in the crystal. Moreover, the solid-state reaction environment traps a highly unstable intramolecular photodimer conformation which defies the conventional wisdom surrounding conformational polymorphs. These observations suggest that solid-state reaction chemistry represents an under-appreciated strategy for producing polymorphs that would likely be unobtainable otherwise.

In this work the synthesis of five new Bronsted acidic ionic liquids (BAILs) bearing same anion (camphorsulfonate) but different cations; 3-(3-sulfopropyl)-imidazolium, 1-methyl-3-(3-sulfopropyl)-imidazolium, 1-methyl-3-(4-sulfobutyl)-imidazolium, 1-ethyl-3-(3-sulfopropyl)-imidazolium, 1-butyl-3-(3-sulfopropyl)-imidazolium) were synthesized and characterized. The characterization of BAILs was carried out using NMR, FTIR and elemental analysis (CHNS). The thermophysical properties of these ILs such as density, refractive index, viscosity and thermal stability were analyzed in wide temperature window. Furthermore, the effect of alkyl chain length of cations on thermophysical properties was well studied. The experimental values of density were further used to calculate other significant properties such as molar volume, standard molar entropy, lattice energy and thermal expansion coefficients. The Bronsted acidities of investigated ILs were determined using Hammett method. Furthermore, COSMO-RS study was performed to determine δ-surface, and δ-profile of the studied ILs.