Search

In this paper, electronic and structural properties such as lattice constant, energy band structure, and density of states of InP in bulk and nanowire are calculated. The calculations have been performed using the Pseudopotential method in the framework of density functional theory (DFT) with local density approximation (LDA), and generalized gradient approximation (GGA) by Quantum Espresso package. The results show a direct bandgap of 1.4 eV at the Γ point in the Brillouin zone and have not cut the Fermi level, with a good agreement with the available experimental results. Also, band structure in nanowires of about 1.49 eV was calculated, which shows an increased bulk state. The calculated results show good agreement with the available experimental results.

The structure and electrical resistivity of Na1-xRbx binary alloys (where x = 0, 0.1, 0.2,…,1) are computed using Percus-Yevick (PY) equation, hard-sphere model and Faber-Ziman formula respectively. The partial structure factors and total structure factor are computed using hard-sphere model for Na1-xRbx. In the calculation of resistivity using Faber-Ziman formula, we have employed Ashcroft empty-core pseudo-potential and Hartree dielectric screening. Calculated values of resistivity are compared with the experimental results and other theoretical values reported in literature. It is found that the electrical resistivity calculated using Faber-Ziman formula for binary alloy Na1-xRbx is in good agreement with the values reported experimentally.

A multiphase Lattice Boltzmann model with phase change is presented for studying droplet impact and solidification on an airfoil. The proposed model combines a pseudo-potential multiphase model and a thermal single-component phase change model. These two models are verified separately. The pseudo-potential model with the Peng–Robinson equation of state is used to simulate large density ratios of multiphase flows. The thermal model is based on the total enthalpy and allows the phase change without using an iterative methodology. The coupling is made through the immersed moving boundary method that handles the solid–liquid interface. The generalization for curved surfaces is introduced through to a novel extrapolation method at boundaries. The effects of surface wettability, static contact angle and initial velocity of the droplet on the evolution of solid fraction and total freezing time are discussed and compared to other simulation and experimental works.

The influence of dynamic contact angle on flow boiling in vertical ducts is investigated based on the phase-change lattice Boltzmann method (LBM). To verify the correctness of the model, the surface tension of bubbles is calculated by the Laplace law and compared with the actual values. The influence of different contact angle on flow boiling is discussed. The mechanisms of bubble growth time and bubble waiting time on different contact angle surfaces are discussed. The heat transfer coefficient of different surfaces is investigated. The simulation results show that the boiling heat transfer characteristics on hydrophilic surface is better than that on hydrophobic surface. [ABSTRACT FROM AUTHOR]

In this paper, a multi-relaxation time (MRT) pseudo-potential based lattice Boltzmann model is implemented to investigate the isothermal injection filling of 2D cavities with arbitrary shapes. The model is capable of handling relatively large density ratios and low viscosities. First, the model is validated by a comparison of the numerical results with those of the experiments reported in the literature for a broken dam problem where a good agreement is observed. Next, the filling process of a rectangular cavity is simulated and effects of the Reynolds and Froude numbers as well as the cavity aspect ratio are investigated. Two filling regimes namely steady and splashing are identified. The formation of gas bubbles are observed in the splashing regime while in the case of steady filling, no bubbles are trapped and the liquid jet fills the cavity smoothly. Furthermore, the threshold Re number for the onset of splashing is evaluated by changing the effective variables. It was found that this threshold Re is increased by a reduction of the cavity aspect ratio ( H / L ) less than 0.5. Decreasing the Fr number and increasing the ratio D / L also increase the threshold Re for the onset of splashing. In the next case, filling a circular cavity with a solid core is also simulated at relatively low and high Re numbers and results at a Re of 81 are compared with those of the SPH method reported in the literature. Finally, a multi-branch header discharging into eight uniform cavities is studied. It was found that the filling sequence of the branches is different for low and relatively high Re numbers. [ABSTRACT FROM AUTHOR]

Via ab-initio approximations, we investigate the electronic and structural features of the CsRb molecule. Adiabatic potential energy curves of 26 1,3 Σ + , 18 1,3 Π and 6 1,3 Δ electronic states with their derived spectroscopic constants as well as vibrational levels spacing have been carried out and well explained. Our approach is founded on an Effective Core Potential (ECP) describing the valence electrons of the system. Using a large Gaussian basis set, the full valence Configuration Interaction can be applied easily on the two-effective valence electrons of the CsRb system. Furthermore, a detailed analysis of the electric dipolar properties has been made through the investigation of both permanent and transition dipole moments (PDM and TDM). It is significant that the ionic character connected with electron transfer that is linked to Cs + Rb − state has been clearly illustrated in the adiabatic permanent dipole moment. [ABSTRACT FROM AUTHOR]

An ab initio investigation has been performed for the ground and several excited states of Ca + He and CaHe systems. The potential energy curves, spectroscopic constants, vibrational levels energies and electric dipole moments have been calculated and analyzed. The ab initio method uses the pseudo-potentials technique, Core Polarization Potentials (CPP) and Full Configuration Interaction (FCI). The number of active electrons of Ca + He and CaHe are reduced to one and two active electrons, respectively. The examination of these numerous results shows interesting structures and behaviors resulting from a collision-induced process that involves calcium and helium atoms. An excellent agreement is found with the available results which confirms the reliability of our calculation. [ABSTRACT FROM AUTHOR]

We have studied how electrons, initially in thermal equilibrium, drift under the action of an applied electric field within bulk zincblende InAsxP1-x, InAs and InP. Calculations are made using a non-parabolic effective-mass energy band model. Monte Carlo simulation includes all of the major scattering mechanisms. The band parameters used in the simulation are extracted from optimised pseudo-potential band calculations to ensure excellent agreement with experimental information and ab-initio band models. The effects of alloy scattering on the electron transport physics are examined. For all materials, it is found that electron velocity overshoot only occurs when the electric field is increased to a value above a certain critical field, unique to each material. This critical field is strongly dependent on the material parameters. Transient velocity overshoot has also been simulated, with the sudden application of fields up to 1600 kVm-1, appropriate to the gate-drain fields expected within an operational field-effect transistor. The electron drift velocity relaxes to the saturation value of about 1.5105 ms-1 within 4 pico-seconds for all crystal structures. The steady-state and transient velocity overshoot characteristics are in fair agreement with other recent calculations.

In this paper we discuss Bäcklund transformations with two pseudo-potentials. We obtain two such transformations, one of which is from the modified KdV equation to itself, and the other from the modified KdV equation to another known nonlinear equation. As applications, from the trivial solutions of the modified KdV equation, we construct some novel solutions. [ABSTRACT FROM AUTHOR]

The structural and electronic properties of (SrLi)+molecular ion have been determined by the use ofab initioapproaches. Potential energy curves (PECs) with their spectroscopic constants (Re,De, ωe,Te,Beand ωeχe) have been calculated. Also, the vibrational properties and the electric dipole moments, either permanent (PDM) or transition (TDM) ones, have been investigated and analysed. Large Gaussian basis sets, the full valence configuration interaction (FCI) and the formalism of non-empirical pseudo-potential including the two approaches, effective core potential (ECP) and core polarisation potential (CPP), are analysed. Therefore, (SrLi)+is considered as a two effective electrons system. Numerous excited states of symmetries1,3Σ+,1,3Π and1,3Δ dissociating below the ionic limit Sr2+Li−have been investigated. This study shows interesting behaviours around the avoided crossing related to charge transfer involving important processes in physics and astrophysics such as dynamics, pre-dissociation and inelastic transitions. [ABSTRACT FROM AUTHOR]

In this paper, a single-component multiphase pseudo-potential lattice Boltzmann model is developed to study droplet impact onto a thin liquid film in 2D coordinates. The model has certain capabilities which make it applicable to cases with large density ratios as high as 1000, low viscosities, and tunable values of surface tension independent of the density ratio. The coexistence values (densities) from the numerical model are compared to those of the analytical solution of the Maxwell construction. For further validation of the model, the simulation results for pressure difference at the droplet interface for various radii are compared to those of the theoretical solution based on the Laplace law. A test on an oscillating droplet is also performed for two different surface tension values to evaluate the ability of the model in simulating dynamic cases such as droplet impact. Next, the model is used to study a droplet impact onto a thin liquid film. It was found that the propagation rate of non-dimensional crown radius obeys the power law reported in the literature. Finally, effects of the surface tension (characterized as Weber number), the gas kinematic viscosity and the density ratio of liquid to gas on a droplet impact onto a thin liquid film are investigated. Results show that increasing the Weber number leads to more crown height causing more instability of the rim, and eventually generation of satellite droplets from the crown tip. Results of changing the gas kinematic viscosity revealed that at high density ratios such as 1000 selected in this paper, when the kinematic viscosity ratio of the gas to liquid is high (above 150), no satellite droplets are produced during the considered time. For a case with a low density ratio of 10, the raised liquid from the surface is not permitted to move freely in radial and vertical directions leading to the formation of an inward liquid turn on top of the raised liquid sheet. Therefore, the crown-shape liquid rise formed at high density ratios is not observed in a case of low density ratio. [ABSTRACT FROM AUTHOR]

The source function (SF) is a topological descriptor that was introduced and developed by C. Gatti and R.W. Bader in 1998. The SF describes the contribution of each atom to the total electron density at a given point. To date, this descriptor has only been calculable from electron densities generated by all-electron (AE) methods for the investigation of single molecules or periodic systems. This study broadens the accessibility of the SF, offering its calculation from electron densities generated by plane wave (PW) methods. The new algorithm has been implemented in the open source code, CRITIC2. Our novel approach has been validated on a series of test systems, comparing the results obtained at PW level with those previously obtained through AE methods. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In this research, the use of the exact difference method forcing scheme in the pseudo-potential multiphase model is suggested for the simulation of a droplet impact on a thin liquid film at a density ratio of 1000, and the effect of inertia, surface tension, and gravity forces are considered by means of their corresponding non-dimensional numbers (i.e. the Reynolds, Weber, and Bond numbers). For this reason, the Palabos open source software is modified by implementing the exact difference method in it. The results of our simulations in different Reynolds and Weber numbers show that the Weber number has a slight influence on the crown layer radius, meanwhile, the Reynolds number has a direct effect on the crown radius. The crown height is increased with an increase in the Reynolds and Weber numbers. Furthermore, the comparison between the pseudopotential model simulations and the free-energy model shows that crown shape is related on the surface tension in addition to the non- dimensional numbers and with a noticeable increase in surface tension the crown tip becomes bigger. The influence of the gravity force is investigated through the Bond number. According to the results, the crown height is noticeably affected by the Bond number. When the Bond number decreases, the crown radius and height increase. Therefore, the proposed model with the capability of being used for multiphase problems with large density ratios while producing a low spurious current could be utilized for a vast variety of other multiphase problems as well. [ABSTRACT FROM AUTHOR]

In this study a computational method of the multi-reference VCA (virtual crystal approximation) pseudo-potential generation is presented. This is an extension of that proposed by Ramer and Rappe (2000), the scheme of which is in want of the explicit incorporation of semi-core states. To compensate this drawback, a kind of fine tuning is applied to the non-multi-reference VCA pseudo-potential; the form of the pseudo-potential is slightly modified within the cut-off radius in order that the agreements between the pseudo-potential and all-electron calculations are guaranteed both for semi-core and valence states. The improvement in the present work is validated by atomic and crystalline test calculations for the transferability and the lattice constant estimation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two different ab initio methods, viz., pseudo- and full-potential based are used. [•] Phase transition has been studied from B1 to B2 phase. [•] Electronic behaviour has been studied in B1 and B2 phases for the first time. [•] Mechanical and thermal properties are studied systematically for the first-time. [ABSTRACT FROM AUTHOR]

X-ray absorption near-edge spectroscopy (XANES) spectra of solid and liquid iron at pressure and temperature obtainable at the Earth's mantle conditions have been calculated. The spectra have been obtained using the supercell with an electron core-hole approach, in anab initioscheme based on the continued-fraction approach and norm-conserving pseudo-potentials. The atomic structures for the spectra calculations were obtained from classical molecular dynamics simulations performed using an optimized modified embedded-atom potential. Comparisons to experimental XANES data are made for both solid and liquid phases of iron. For the liquid configuration, we find excellent agreement. Calculated spectra obtained for the solid configurations are also in good agreement with the experiment, and those obtained via other theoretical methods. We discuss the electronic origin of the XANES features. [ABSTRACT FROM PUBLISHER]

Nonlinear dust ion acoustic solitary waves (DIASW) in dusty plasma are studied incorporating kinematic viscosity, using Sagdeev's pseudopotential approach. The effects of kinematic viscosity and the nonextensive parameter q on the features of DIASW are investigated in some detail. [ABSTRACT FROM AUTHOR]

The potential energy curves have been calculated for the electronic states of the molecule LiK within the range 3 to 300 a.u., of the internuclear distance R. Using an ab initio method, through a semiempirical spin-orbit pseudo-potential for the Li (1 s) and K (1 s2 s2 p3 s3 p) cores and core valence correlation correction added to the electrostatic Hamiltonian with Gaussian basis sets for both atoms. The core valence effects including core-polarization and core-valence correlation are taken into account by using an l-dependent core-polarization potential. The molecular orbitals have been derived from self-consistent field (SCF) calculation. The spectroscopic constants, dipole moments and vibrational levels of the lowest electronic states of the LiK molecule dissociating into K (4 s, 4 p, 5 s, 3 d, and 5 p) + Li (2 s, 2 p, 3 s, and 3 p) in Σ, Π, and Δ symmetries. Adiabatic results are also reported for Σ, Π, and Δ electronic states of the molecular ion LiK dissociating into Li (2 s, 2 p, 3 s, and 3 p) + K and Li + K (4 s, 4 p, 5 s, 3 d, and 5 p). The comparison of the present results with those available in the literature shows a very good agreement in spectroscopic constants of some lowest states of the LiK and LiK molecules, especially with the available theoretical works. The existence of numerous avoided crossing between electronic states of Σ and Π symmetries is related to the charge transfer process between the two ionic systems LiK and LiK. [ABSTRACT FROM AUTHOR]

Abstract: Structural, electronic, mechanical and thermo-physical properties of refractory carbides (TiC, ZrC and HfC) have been investigated in the stable B1 as well as high pressure B2 phase along with the high pressure phase transition in these materials by two different pseudo- and full-potential approaches. The results are compared with experiments to adjudge the effectiveness of both approaches. Band structure and DOS calculations provide evidence for metallic (finite DOS at EF) and covalent (C (p)–TM (d) hybridization) bonding in these materials in both phases. Ionic bonding is also revealed from charge density plots. Covalent nature dominates in B1 phase while ionic bonding in B2 phase. The elastic constants show the mechanical stability of these carbides in B1 phase and instability in B2 phase. These materials are brittle and anisotropic in B1 phase. Elastic wave velocities and the Debye temperatures have also been reported. The present results show good agreement with the measured data. However, some of the calculations are reported for the first-time. [Copyright &y& Elsevier]

The problems of large amplitude double layers are discussed using Sagdeev's pseudo-potential technique for a dusty plasma comprising two temperature isothermal ions and nonextensive nonthermal velocity distributed electron. For different sets of plasma parameter values, the Sagdeev potential V( ϕ) has been plotted. It is found that nonextensive q parameter plays a significant role in determining the shape and size of large amplitude double layers. Also, it is observed that the existence of large amplitude double layers depends on different plasma parameters. [ABSTRACT FROM AUTHOR]

Dust acoustic double layers are studied in a four component dusty plasma comprising positively and negatively charged dust grains, Boltzmann distributed ions and kappa distributed electrons. The conditions for existence of double layers are studied in detail using Sagdeev's method. Large amplitude double layers are obtained for a range of values of the plasma parameters. [ABSTRACT FROM AUTHOR]

Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels have been computed for the lowest electronic states of alkali dimers LiX and NaX (X = Rb, Cs). Calculations have been carried with the use of an ab initio approach with core‐potential potentials and full‐valence configuration. Thus, these systems are treated as two‐electron systems. A good agreement is obtained for some lowest states of the molecules studied with available theoretical works. The existence of numerous avoided crossings between electronic states for 1Σ symmetries is related to the charge‐transfer process in each molecule between its two ionic systems (Li+X−, Li−X+) and (Na+X−, Na−X+). © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: For all states dissociating below the ionic limit Li−K+, we perform an adiabatic and diabatic study for electronic states dissociating into K (4s, 4p, 4d, 5s, 5p, 5d, 6s)+Li (2s, 2p, 3s). Furthermore, we present the adiabatic results for the 1–11 , 1–8 and 1–4 states. The present calculations on the KLi molecule are complementary to previous theoretical work on this system, including recently observed electronic states that had not been calculated previously. The calculations rely on an ab initio pseudo-potential, Core Polarization Potential operators for the core–valence correlation and full valence CI approaches, combined to an efficient diabatization procedure. For the low-lying states, our spectroscopic constants and vibrational level spacing are in good agreement with the available experimental data. Diabatic potentials and permanent dipole moments are analyzed, revealing the strong imprint of the ionic state in the adiabatic states. [Copyright &y& Elsevier]

Abstract: Pseudo-potentials for diatomic molecules can be interpolated to high accuracy with a high order Hermite spline via the function Y =−[(ES − EU )/EU ]EE [(1− z)/2]2 where ES is the energy of the separated atoms, EU the united atom energy, EE the electronic energy and z = (R − Ra )/(R+Ra ), where R is the inter-nuclear distance and Ra is an adjustable parameter. Both Y and its derivative with respect to z are very smooth, which facilitates the interpolation process. Limiting laws are used at each end to provide spline constraints and also to replace the spline in the regions beyond the data, giving a hybrid result. The low R limiting law is of the form EE = EU + Σi =2 Ai R i. The A coefficients are obtained by least-squares. The high R limiting law is of the form E = ES - ΣCi ; the C coefficients can be obtained from perturbation theory, least-squares or in combination. Test data with a pseudo-potential similar to that of most diatomic molecules with added noise was interpolated with an order 12 spline at data intervals of 0.05, 0.1 and 0.2 Bohr. The resulting maximum errors in E− i ; the C coefficients can be obtained from perturbation theory, least-squares or in combination. Test data with a pseudo-potential similar to that of most diatomic molecules with added noise was interpolated with an order 12 spline at data intervals of 0.05, 0.1 and 0.2 Bohr. The resulting maximum errors in EE and vibrational energy levels were no more than several times a noise level of 10−17, 10−15 and 10−10, respectively. The lowest noise level at which the maximum errors were acceptable decreased with data range, spline order and smoothness of the function. The interpolation procedure was successfully applied to the H2 X, C and a states, for which abundant data in the form of tables of energy and gradient are available. [ABSTRACT FROM AUTHOR]

Abstract: Damage pseudo-potentials, from which the damage evolution equations can be acquired, are usually expressed as scalar functions of irreversible thermodynamic variables. A lower potential for an action with the dissipation property corresponds to a Helmholtz free energy function in classical mechanics; therefore, pseudo-potential acts as a cornerstone of the damage constitutive relationship. According to the analysis on state and process of a damage system, the authors study the connection between damage action, pseudo-potential and free energy function. Next a general method to define the pseudo-potential of damage process is discussed. The discrete elementary equations of continuum damage mechanics are derived from the action functional. Subsequently, the numerical implementation of the aforementioned damage model is given. Comparison between experimental evidences and numerical results verifies the soundness of the theoretical model and the numerical framework. [Copyright &y& Elsevier]

Dust acoustic double layers are studied in a four component dusty plasma. Positively and negatively charged mobile dust and Boltzmann distributed electrons are considered. The ion distribution is taken as nonthermal. The existence of compressive and rarefractive double layers is studied by pseudopotential approach. The effect of non-thermal ions on small amplitude and arbitrary amplitude double layers are also studied. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional condensation in a domain filled with metal foam is investigated using the lattice Boltzmann method for the first time. A recently proposed two-phase pseudo-potential lattice Boltzmann model is extended to 3D phase-change problems by adding the energy equation with the Peng–Robinson equation of state. The phase-change model is validated using the thermodynamic consistency test, Laplace law, contact angle test, and D 2 -law. To provide accurate pore-scale analysis, both the flow and energy equations are discretized with the D3Q27 model. Moreover, the metal foam cell structure is reconstructed by implementing the Lord Kelvin model on the mesh nodes. The results are reported in terms of condensation modes, droplet nucleation, growth and removal, heat flux on the walls and mass flow rate of the discharged condensate. Furthermore, the effects of the Jakob number (in range of J a = 0. 06 to 0.24) and cell size (S = 16 , 32 , and 64) are investigated regarding the condensation process, average heat flux, and mass flow rate. The condensation curve under constant temperature boundary condition is presented for different configurations. It is shown that the model is capable of simulating convection heat transfer along with different condensation modes, including dropwise and filmwise modes. Our results revealed that the onset of nucleation and mode transition occurs at lower Jakob values as the metal foam cell size is increased. Also, it is shown that at a fixed configuration, increasing the Jakob number affects the condensate mass flow rate more than heat flux. The results of this study could be useful in the design of phase-change heat exchangers with metal foam construction. • Three-dimensional simulation of condensation in metal foam media is done using LBM. • Convection, nucleation, dropwise, and filmwise modes are observed. • Lower PPI initiates nucleation & dropwise–filmwise transition at lower Jakob values. • At a fixed Jakob value, higher PPI can enhance heat flux with lower condensed mass. [ABSTRACT FROM AUTHOR]

Abstract: The structural and electronic properties of Co4Si4− x Ge x (x=0–4) compounds are investigated using density functional theory (DFT). The calculations are based on a plane-wave expansion of the electronic wave functions using pseudo-potential method and performed using the local density approximation (LDA). It is found that these compounds are semimetals with a slight overlap between valence and conduction bands. The tendency towards metallic behavior of the compounds increases in terms of Ge concentration. [Copyright &y& Elsevier]

In this paper, we have studied theoretically the effects of gold adsorption on the Al(001) surface, using ab initio pseudo-potential method in the framework of the density functional theory. Having found the hollow sites at the Al(001) surface as the most preferred adsorption sites, we have investigated the effects of the Au adsorption with different coverages (Θ =0.11, 0.25, 0.50, 0.75, 1.00 ML) on the geometry, adsorption energy, surface dipole moment, and the work function of the Al(001) surface. The results show that even though the work function of the Au substrate increases with the Au coverage, the surface dipole moment decreases with the changes in coverage from Θ =0.11 to 0.25 ML. We have explained this behavior by analyzing the electronic and ionic charge distributions. Furthermore, by studying the diffusion of Au atoms into the substrate, we have shown that at room temperature the diffusion rate of Au atoms into the substrate is negligible but increasing the temperature to about 200°C the Au atoms significantly diffuse into the substrate, in agreement with the experiment. [ABSTRACT FROM AUTHOR]

Ashcroft’s empty core (EMC) model potential is used to study the superconducting state parameters (SSPs) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature T C , isotope effect exponent αand effective interaction strength N O V of some binary metallic glasses based on the superconducting (S), conditional superconducting (S’) and non-superconducting (NS) elements of the periodic table. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used for the first time with EMC potential in the present investigation to study the screening influence on the aforesaid properties. The T C obtained from the H-local field correction function are in excellent agreement with available theoretical or experimental data. In the present computation, the use of the pseudo-alloy-atom model (PAA) was proposed and found successful. Present work results are in qualitative agreement with such earlier reported experimental values which confirm the superconducting phase in all metallic glasses. A strong dependency of the SSPs of the metallic glasses on the valence ‘Z’ is identified. [ABSTRACT FROM AUTHOR]

In this paper, we focus on uniaxial and biaxial strain technologies, and we also investigate an optimum combination of strain method and channel direction. We linked the first principles band calculation program to the FUJITSU ensemble full band Monte Carlo simulator FALCON directly, which enables to incorporate arbitrary Si band structures such as uniaxial and biaxial strained-Si into device characteristics analysis. We show that the combination of biaxial tensile strain and <100> current for NMOS, and compressive uniaxial strain and <110> channel for PMOS are optimum methods for current enhancement. However, considering technological difficulties and process cost, it is one of the candidate methods to use the combination of uniaxial tensile strain and <100> channel direction for NMOS and that of uniaxial compressive strain and <110> channel direction for PMOS. [ABSTRACT FROM AUTHOR]

Abstract: The adaptation rule of Vector Quantization algorithms, and consequently the convergence of the generated sequence, depends on the existence and properties of a function called the energy function, defined on a topological manifold. Our aim is to investigate the conditions of existence of such a function for a class of algorithms including the well-known ‘K-means’ and ‘Self-Organizing Map’ algorithms. The results presented here extend several previous studies and show that the energy function is not always a potential but at least the uniform limit of a series of potential functions which we call a pseudo-potential. It also shows that a large number of existing vector quantization algorithms developed by the Artificial Neural Networks community fall into this class. The framework we define opens the way to studying the convergence of all the corresponding adaptation rules at once, and a theorem gives promising insights in that direction. [Copyright &y& Elsevier]

Abstract: Some minimum theorems potentially useful to construct numerical schemes related to quasi-static evolution of damage in brittle elastic solids are proposed. The approach is that of multifield theories, with a second-order damage tensor describing the microcrack density. The use of damage entropy flux and damage pseudo-potential are both investigated. [Copyright &y& Elsevier]

The interest in first principles investigations of metal-oxide surfaces has been growing rapidly over the past 10 years. Several phenomena of vital importance for fundamental understanding of heterogeneous catalysis have been investigated, including the metal/metal-oxide interface and the interaction with adsorbates. This contribution reviews different implementations of the density functional theory frequently used in studies of metal-oxide properties. Computational results are discussed and compared to experimental data. [ABSTRACT FROM AUTHOR]

• Spectroscopic investigation is carried out in the adiabatic representations (PECs, PDM, TDM). • Illustration of the ionic character and the strong couplings between the excited states. • Spectroscopic parameters and vibrational level spacings are obtained by resolving the radial Schrodinger equation. A non-relativistic description of the electronic structure for the heteronuclear molecule KRb was developed through the Full Configuration Interaction (FCI) and pseudo-potential method. Below the ionic limit K−Rb+, the ground and all excited singlet and triplet states of different symmetries Σ+, Π and Δ (in the Hund's case (a): 2 s + 1Λ±) were intensively investigated. Several adiabatic results including potential energy curves (PECs), permanent and transition electric dipole moments (PEDM, TEDM) were analyzed in short and long-range of internuclear distances. Tables of these properties as functions of separation are presented. The spectroscopic constants with the vibrational levels were derived using the "Numerov" algorithm. These molecular parameters were compared with those published in the literature, feature a good agreement. In the adiabatic representation, strong couplings between successive 1Σ+ states were reached by series of avoided crossing, yielding to the appearance of the ionic character and the good illustration of charge transfer. This description of the KRb molecule was helpful in the design of the prospect photo-association experiments and the obtaining of the quantum-degenerate gas of the polar molecule. [Display omitted] [ABSTRACT FROM AUTHOR]

Using ab-initio adiabatic calculation, we studied the electronic properties of the LiNe molecule. In our calculation, we investigate the adiabatic potential energy curves (PECs) of numerous 2Σ+, Π and Δ electronic states. Then, we derive spectroscopic constants, as well as their vibrational levels spacing. For the 2Σ+ states, we determined the permanent and transition dipole moment (PDM and TDM). Our approach is based on the full configuration interaction (FCI), an effective core potential (ECP) which describes the valence electron of the molecule, and the core polarization potential (CPP). Using a large Gaussian basis set, a full configuration interaction is easily carried out. [ABSTRACT FROM AUTHOR]

Energy of electronic subsystem of semi-infinite metal is presented in the form of an expansion in powers of pseudo-potential. It is shown that generally electron many-particle density matrices are necessary for the energy calculation, whereas in case of a local pseudo-potential only diagonal elements (electron distribution functions) are necessary. In a specific case of a local pseudo-potential within the first order of perturbation theory, our results for energy coincide with those widely applicable in the density functional theory.

Ab-initio calculations are performed to investigate the effect of defects on structural, electronic and optical properties of Ag 8-x Cu x I 8 (0 ≤x ≤ 8). Initially AgI geometrically optimized and Ag atoms are replaced successively by Cu atoms. AgI is thermodynamically most stable, it exhibits low defect formation energy and fast ion conduction. The forbidden energy gap successively decreases with x. There is higher Ag+ ions formation than Cu+ ions. In the optical study, by increasing x, peaks of imaginary and real dielectric functions are shifted towards lower frequency regions, with Ag/Cu defects, there is slight shifting towards higher energy region, gradual increase in refractive index, and the reflectivity peaks are shifted towards higher energy. [ABSTRACT FROM AUTHOR]

In this article, electronic and phononic properties of TiC bulk and its narrow nanowires are calculated by using Quantum-Espresso/PWSCF computational package in the framework of density functional theory. According to the results, this compound shows a metallic behavior in the bulk structure, but for the smallest diameters of the nanowires, against the bulk, a semiconducting behavior was observed. This deviation becomes negligible at higher diameters. In the following, phonon calculations have been performed on bulk and the first diameter of nanowires with a square cross-section. By calculating the phonon modes of Brillouin zone, the thermodynamic properties of both mentioned structures such as vibrational free energy, the heat capacity Cv , Debye temperature Θ , entropy and their variations against temperature T have been obtained through the quasi-harmonic Debye model. Calculations show that heat capacity behavior of the vibrational lattice is consistent with Debye model. Moreover, the temperature dependence of a Debye temperature indicates that the Debye stiffness in a bulk is greater than the nanowire structure. [ABSTRACT FROM AUTHOR]

Spin polarized structural, electronic and magnetic properties of new quaternary Heusler alloy CoZrIrSi have been studied using the first-principles calculation based on density functional theory. Interchanging the positions of atoms, the calculations were performed for three types of Heusler alloy CoZrIrSi. The results clearly showed that all three types of Heusler alloy CoZrIrSi were structurally stable in ferrimagnetic phase and their total spin magnetic moments (μ t = 2μ B /cell) were in accordance with Slater-Pauling rule. Based on investigation of structural properties of Heusler alloy CoZrIrSi, it was found that the type 2 structure of CoZrIrSi was more stable than others due to its lowest cohesive energy. Based on the results of studies undertaken on electronic properties of Heusler alloy CoZrIrSi using GGA-PBE calculations, it was clearly seen that the type 2 structure possessed half-metallic characteristic due to overlapping between conduction and valance band at the Fermi level only for spin-down channel. Thus, type 2 structure of CoZrIrSi had 100% spin polarization. It can be considered a good candidate for spintronics applications. • Three types of quaternary Heusler alloy CoZrIrSi were ferrimagnetic. • The type 2 structure had half-metal characteristic with 100% spin polarization. • The total spin magnetic moment of three types of Heusler alloy CoZrIrSi, was found in compliance with Slater-Pauling rule. [ABSTRACT FROM AUTHOR]