Search

Density functional theory with pesudo potential approximation is used to study XBaB (X = Li , Na, K) half-Heusler compounds structural, magnetic and electrical property using Quantum espresso code and thermoelectric properties were studied using BoltzTrap code. Total energy calculations were carried out in the α , β and γ phases of XBaB compounds in C 1 b type structure. The compounds were stable in α -phase and hence further calculations were focused only on α phase. From the spin polarization calculations, magnetic state was stable than nonmagnetic state and exhibits ferromagnetism at the equilibrium lattice constant with an integer magnetic moment of 2  μ B . From the band structure calculations and through density of states, all the three compounds exhibit half-metallicity with 100% spin polarization by showing semi-conductivity for majority spin and metallicity for minority spin. In addition, thermoelectric properties were investigated for all three compounds. LiBaB is found to have high Seebeck coefficient of 2462 μ VK − 1 and ZT value of 1, compared to other compounds. These materials were found to have high ZT value and hence they can be used for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The full electronic band structure of the Al doped ZnO films have been characterized using the TNL-FB™ (full band) simulator from Tech Next Lab. The bandgaps obtained through simulation studies were matched against the experimental bandgap and compared with the results obtained through DFT-based techniques. It was observed that the bandgap value at the Γ-valley increases with the increase in the Al dopant content from 0 at% to 5 at%. The extracted cut-off absorption wavelength was shifted to a shorter wavelength by increasing the Al content, and justifies the Burstein–Moss shift effect. In the present study, the dependency of the topology of the shape of the nanostructure films was taken care of through the lattice disorder effect. The influence of thickness and plane orientation on the various features has been carefully studied. The full electronic band structures of ZnO and AZO samples predicted that the bandgap value is strongly dependent on the internal structure parameter, u. The value of u is significantly affected by lattice disorder generated due to bond angle or length alteration dependent on the topology of the structure and impurity addition. Good agreement was found between the reported and experimental optical bandgap results. [ABSTRACT FROM AUTHOR]

A novel two-dimensional (2D) half-Heusler ZrNiSn nanosheet for thermoelectric applications was designed from bulk half-Heusler ZrNiSn through first-principles calculation. Investigation of bulk half-Heusler and 2D nanosheet ZrNiSn was performed with the Quantum Espresso code based on a density functional theory plane wave basis set. Electronic band structure and density of states calculations were used to study the confinement effects. On moving from bulk to 2D a change of structure is observed from face-centered cubic to trigonal due to confinement effects. The semiconducting nature of bulk ZrNiSn is undisturbed while moving to a 2D nanosheet; however, the band gap is widened from 0.46 to 1.3 eV due to the restricted motion of electrons in one direction. Compared with bulk ZrNiSn, 2D nanosheets were found to have a higher Seebeck coefficient a lower thermal conductivity and higher figure of merit, which makes 2D ZrNiSn nanosheets suitable for thermoelectric applications. Atomically thin 2D structures with a flat surface have the potential to form van der Waals heterojunctions, paving the way for device fabrication at the nanoscale level. [ABSTRACT FROM AUTHOR]

In molten metals, the atomic dynamics have been studied in the present study with the help of equations of motion in terms of the velocity autocorrelation function (VACF), power spectrum $ G(\omega) $ G (ω) , and mean square displacement $ {r^2}(t) $ r 2 (t). The pair correlation function $ g(r) $ g (r) is used to produce VACF for molten metals in the current study with the help of three different types of structure factor methods i.e. hard sphere Yukawa (HSY) method, optimised random phase approximation (ORPA) method and charged hard sphere (CHS) method. The presently obtained results for molten metals of different groups like Na (Z = 1), Mg (Z = 2), Al (Z = 3), Sn (Z = 4), and Sb (Z = 5) are compared with the molecular dynamic (MD) study and also with the other theoretical data available in the literature. For the present study, our own developed pseudopotential has been used for the calculations of the above-mentioned properties. The screening effect is also been observed over and beyond the bare ion potential with Hartree (H) and the effects of exchanges and correlation were computed using procedures given by Taylor (T) and Nagy (N). [ABSTRACT FROM AUTHOR]

Our recently evolved pseudopotential is used to study the electrical transport properties such as electrical resistivity ($\rho $ ρ), thermal conductivity ($\sigma $ σ) and thermoelectric power ($TEP$ TEP) of some monovalent (Li, Na, K, Rb, Cs), divalent (Mg, Zn, Ca) and polyvalent (Al, Ga, In, Pb, Sn, Bi, Sb) liquid metals. The model potential theory in conjunction with Ziman, mean free path, t-matrix, and Kubo models are implemented in the above-mentioned work for the first time. The Taylor's local field correction function (T) is taken for observing the exchange and correlation effect with one component plasma (OCP) structure factor method of liquid metals with Hartree dielectric function (H). The presently computed findings are extremely comparable with available data, either theoretical or experimental results that exist in the literature. [ABSTRACT FROM AUTHOR]

We introduce a numerical method to solve the two-dimensional time-dependent Schrödinger equation, which characterizes a system of two atoms with a finite-range interaction potential confined within a harmonic oscillator trap. We choose a Gaussian-shaped potential for the interaction potential. Such a system has been previously studied analytically, except that a zero-range interaction potential was used instead. We observe a strong agreement between the results for the two types of interactions. Also, we investigate the one-dimensional time-dependent Schrödinger equation for the relative motion and compute the ground state energy level as a function of the coupling strength.

The collective motions are studied using a recently created pseudopotential and some elastic constants. This paper involves the calculations of the collective motions like phonon dispersion curves (PDCs) for longitudinal and transverse frequencies (ωL and ωT), longitudinal sound velocity (vl), transverse sound velocity (vt), isothermal bulk modulus (B), modulus of rigidity (G), Young’s modulus (Y), Poisson’s ratio (σ), Debye temperature (θD) of some monovalent (Na), divalent (Mg) and polyvalent liquid metals (Al, Pb, Bi). This investigation is based upon the theory of pseudopotential of second-order approach via the equations of Hubbard and Beeby (HB). g(r) The pair correlation function is calculated from the different mean spherical approximation (MSA), one-component plasma (OCP) and optimized random phase approximation (ORPA) structure factors employed in this work. Three different types of local field correction (screening) functions proposed by Hartree (H), Taylor (T) and Nagy (N) are utilized in this paper. The current findings are found to be in qualitative accord with experimental and theoretical data. [ABSTRACT FROM AUTHOR]

The scattering dynamics of electron capture in e+$$ {\mathrm{e}}^{+} $$‐H(1 s) scattering under dense semi‐classical plasma (DSCP) environments has been investigated theoretically. Coupled multi‐channel two‐body Lippmann‐Schwinger equations have been solved by retaining e+$$ {\mathrm{e}}^{+} $$+H(1 s) and p + Ps(1 s) channels to calculate the cross sections (CS) of the electron capture process at intermediate and high incident energies. The effective interaction of the plasma charged particles is modelled by a pseudopotential which is a function of two parameters, namely the plasma screening strength and the de Broglie wavelength. A detailed study is made to explore the changes in the CSs of the above‐mentioned process with respect to the variation in the plasma screening strength and de Broglie wavelength. Significant changes are found to take place, when the screening strength and the de Broglie wavelength are varied. Specifically, the sharp minimum in the differential CS moves toward the forward direction with increasing de Broglie wavelength at a given screening strength. [ABSTRACT FROM AUTHOR]

The first principle of calculation is a computational technique based on quantum mechanics that may precisely determine the ground-state electronic structure and associated mechanical and thermodynamic characteristics of solid materials. This study explains the history of first-principles development, calculation techniques, and the use of ultra-soft pseudopotential in hydrogen storage materials based on an inquiry and analysis of the findings of previous research. This paper primarily reviews the research progress of first principles in improving two-dimensional hydrogen storage materials, metal-organic framework materials, alkali metal-base composite hydrides, and metal-base hydrogen storage materials in order to speculate on the hydrogen storage mechanisms of materials. It is possible to estimate the location of hydrogen adsorption in a material by computing its electronic structure, band structure, electron density, and lattice vibration. This information is then used to compute the hypothetical new hydrogen storage material. Finally, the direction of first-principles computing in hydrogen storage materials is anticipated. • The research progress of DFT in predicting and simulating new hydrogen storage materials is introduced. • The merits and demerits of the application of DFT in solid hydrogen storage and its future development direction are pointed out. [ABSTRACT FROM AUTHOR]

Using the pyrolyzing polymer‐salt compositions method yttrium orthochromite (space group Pnma) was synthesized. A value of oxygen nonstoichiometry δ=.056 and a band gap of 1.64 eV were obtained. With the experimentally determined structural parameters as a basis, we performed ab initio simulations to investigate the defect structure of YCrO3±δ. We studied the presence of interstitial oxygen in the YCrO3 at oxygen nonstoichiometry close to the experimental value and vacancies at the same concentration. Formation energies were estimated for interstitial oxygen atoms and compared with those of oxygen vacancies in the cases neutral and charged supercells. The computational results demonstrate that interstitial oxygen is energetically more favorable than the formation of oxygen vacancies. We considered various configurations of the interstitial oxygen atom within the YCrO3 crystal lattice and identified two fundamentally distinct types. An analysis of projected densities of states and charge distributions was performed for these configurations. The results indicate that direct intercalation of oxygen atoms is energetically more favorable than the formation of a peroxide species when the Fermi level is close to the conduction band minimum. [ABSTRACT FROM AUTHOR]

An elegant calculation is carried out to investigate the effects of the non‐ideality of classical plasma on the energy levels of the hydrogenic atoms held in a spherical cage. Organized effect of the non‐ideal classical plasma is described by an analytical pseudopotential which contains the Debye length D and non‐ideality parameter γ as parameters. Convergent results for the bound states are obtained variationally by utilizing a large trail function containing cosine term which automatically takes care of the requisite boundary conditions. For the plasma‐free case, our results are in excellent agreement with the most accurate results available in the literature. An inclusive study is made to explore the changes emerging in the energy levels due to the variation of the plasma parameters and cage size. Special emphasis is made on the determination of critical cage size precisely. The present study specifically reveals that the increasing plasma non‐ideality leads to the elongation of the critical cage size. Moreover, it is empirically found that the critical cage size for a given hydrogenic atom can be obtained from a scaling law. [ABSTRACT FROM AUTHOR]

Based on the band structure of TlGaTe compound, the extrema of the valence and conduction bands were determined and the tensor of the components of the inverse effective mass of electrons and holes was calculated. [ABSTRACT FROM AUTHOR]

Formerly we created a one-electron local pseudopotential which proved to be successful in studying transport phenomena in various sp2 carbon nanosystems, e.g. graphene grain boundaries and nanotube networks. In this work, we present an extended version of the local pseudopotential which correctly describes the electronic structure of van der Waals stacks of carbon sheets, e.g. AA, AB bi-layer graphene, ABC (rhombohedral) tri-layer graphene, as well as AA, AB, and ABC graphite, etc., even in case of external electric fields. We utilize this potential to study the hopping dynamics of wave packets between the graphene sheets in multilayer systems. The frequency of the hopping is proportional to the band splitting, caused by the interlayer coupling. For the case of AB and ABC graphene there is a backscattering near the Fermi level, causing a Zitterbewegung-like phenomenon, an interference between +kBloch and −kBloch states. For the rhombohedral tri-layer graphene the time dependence of the wave packet probability density is an aperiodic function for the first- and third layer (the two outer layers), but a quasi-periodic function for the second (inner) layer.

The structure property is the fundamental factor in determining the stability, adsorption, catalytic performance, and selectivity of microporous materials. Seven density functional approximations (DFAs) are used to simulate the crystal structure of microporous material for examining the efficiency and accuracy. In comparison with the existing zeolites, microporous materials with CHA framework are selected as the testing model. The calculation results indicate that the least lattice volume deviation is 5.18/2.72 Å3 from PBE_mGGA, and the second least is −5.55/−10.36 Å3 from LDA_PP. Contrary to USPP_LDA, PBE_GW, PAW_PBE, and PAW_GGA overestimate the lattice volume by ~15.00–20.00 Å3. For each method, RMS deviations are less than 0.016 Å for bond length and less than 2.813° for bond angle. To complete the crystal structure calculation, the CPU time reduces in order of USPP_GGA > PBE_GW > PAW_GGA, PBE_mGGA > PAW_PBE > LDA_PP > USPP_LDA. For two testing models, when the calculation time is not important, PBE_mGGA is the best choice, and when the tradeoff between accuracy and efficiency is considered, LDA_PP is preferred. It seems feasible and efficient to simulate the zeolite structure through E-V curve fitting, full optimization, and phonon analysis bythe periodic density functional theory. [ABSTRACT FROM AUTHOR]

We report on the discovery of a contradiction appearing in the solutions to the problems of profiles of the nonlinear longitudinal electrostatic waves in plasma obtained using the Sagdeev's pseudopotential approach. The contradiction reveals itself in the average over period particle concentration and given concentration of the unperturbed plasma being unequal to each other. It is demonstrated that the reason for the appearance of this contradiction is related to the relatively widely spread inaccuracy in the formulation of such problems. It is suggested correcting the formulation of such problems and changing interpretation of solutions obtained using the approach under consideration by imposing different initial conditions: it is necessary specifying particle concentration at the points where potential φ is set equal to zero instead of concentration of the unperturbed plasma. The contradiction is resolved completely when using such initial conditions. [ABSTRACT FROM AUTHOR]

Along with a few elastic constants, a recently created pseudopotential is employed to examine the vibrational properties of some simple alkali metals, i.e. Li, Na, K, Rb and Cs. The phonon dispersion curves (PDC) are computed in the text. (ωL and ωT), longitudinal sound velocity (vl), transverse sound velocity (vt), isothermal bulk modulus (B), modulus of rigidity (G), Young’s modulus (Y ), Debye temperature (θD) of some liquid alkali metals. The second order technique used in the current work, using Hubbard and Beeby (HB) equations, is based on pseudopotential theory. The various Percus-Yevick hard sphere (PYHS) and one-component plasma (OCP) structure factors used in the current investigation are used to construct the pair correlation function g(r). The current paper makes use of three distinct forms of local field correction functions developed by Hartree (H), Taylor (T), and Nagy (N). The current findings are found to qualitatively agree with the experimental and theoretical data that is currently available.

We investigate the low-energy scattering properties of two identical particles interacting via the polarized quadrupolar interaction. It is shown that a series of s - and p -wave resonances appear for identical bosons and fermions, respectively, as the strength of the quadrupolar interaction increases. Interestingly, scattering resonances also appear on the generalized scattering length corresponding to the coupling between the s and d waves. This observation inspires us to propose a new pseudopotential for the quadrupolar interaction. We also explore the bound-state properties of two particles in both free space and harmonic traps. [ABSTRACT FROM AUTHOR]

The lattice-matched system (GaAs)n/(AlAs)n superlattice is calculated for two different values of n=3 and 6 within ab initio pseudopotential density-functional theory using Quantum Espresso package of program exploiting the ultra-soft atomic pseudopotentials. Their band offsets, which is a well-known and inextricable problem at semiconductor interfaces, have been determined in this paper and were compared with experimental results. Discontinuities of valance and conduction bands were obtained as 0.46 and 0.25 eV, respectively. The averaged self-consistent potential across the [001] interface in GaAs is about 0.061 eV higher than its value in AlAs. The local density of states for both superlattices was also studied. The effect of different factors e.g. orientation, transitivity, and composition dependence is reported in this study. We found that, in the [110] direction of GaAs/AlAs superlattice, the dependence of the band offset on the orientation is negligible. The calculated band gap of is linearly dependent on aluminum content.

Based on the calculations from the first principles, we obtained the distributions of valence electron densities and electron energy spectra for a CdS film with different oxygen concentrations. According to the results of calculations, it is established that during the adsorption of oxygen atoms on the surface of CdS, oxygen taking electrons from the surface atoms of the CdS film, increases its catalytic activity. The oxygen concentration should not exceed 12.5%.

Composite methods are the combination of ab initio calculations used to achieve high precision in the face of a computational reduction. Weizmann-n theories (n = 1, 2, 3, and 4) stand out for presenting a high precision, and a version of the W1 theory is the W1BD theory that uses ab initio Brueckner Doubles (BD) methods. One way to reduce the computational cost of composite methods and maintain accuracy is to use pseudopotentials in the calculation steps; in this context, W1BDCEP composite method was developed from the respective W1BD all-electron version by considering the implementation of compact effective pseudopotential (CEP). The test set used to evaluate the theory were 8 proton affinities (PA0), 46 electron affinities (EA0), 54 ionization energies (IE0), 80 enthalpies of formation (ΔfH0), and 10 bond dissociation energies (BDE). The mean absolute deviation values (MADs) for W1BD and for the version adapted to the pseudopotential, W1BDCEP, were similar, with values of 0.97 kcal mol−1 and 1.03 kcal mol−1, respectively, when the properties PA0, EA0, IE0, and ΔfH0 were evaluated together. Comparing the versions of the theories that employ ab initio Brueckner Doubles calculations with the W1 and W1CEP theories, it is possible to observe that the W1BD and W1BDCEP theories are more accurate than the W1 theory (MADW1 = 1.25 kcal mol−1) and W1CEP (MADW1CEP = 1.44 kcal mol−1), proving the accuracy of using the BD method. Pseudopotential reduces computational time by up to 30% and thus enables more accurate calculations with less computational time. [ABSTRACT FROM AUTHOR]

In recent years, the inorganic lead-based perovskites have significant consideration owing to their excellent structural stability. In this work, we explore the structural, electronic, and optical properties of α-CsPbI3 and Ge-incorporated α-CsPbI3 perovskites through first-principle calculations. The 12.5% of Ge-mixed CsPbI3 has pleasant structural stability compared to CsPbI3. The CsPb(1-x)GexI3 band gap is linearly decreased while increasing Ge concentration, and it varied from 1.45 to 1.12 eV. Besides, Ge doped CsPbI3 perovskites have a more substantial absorption coefficient in the visible regions. This result reveals, the Ge-incorporation on the B-site location enhanced structural stability and optical absorption coefficient of CsPbI3. [ABSTRACT FROM AUTHOR]

The problem of sodium and potassium in the attosecond pulse train (APT) as a kicking field is considered. The goal is to investigate the possibility of the kicking field to generate, in general, any secondary radiation. The modifications of the energy bands and the kick-induced currents are examined. Simple local pseudopotentials have been proposed and used. It is demonstrated that the APT generates secondary radiation in a wider spectral range similar to high-order harmonic generation (HHG). This radiation has been found to have a form of periodic complex peak compositions decreasing in intensity with the period approximately equal to the doubled angular frequency of the driving field. This is a new effect. A physical explanation of this effect is given. [ABSTRACT FROM AUTHOR]

Solar radiation, along with cosmic radiation, ionizes the Earth’s atmosphere and creates a dense layer known as the ionosphere. By considering weakly relativistic degenerate plasma in the planetary ionosphere, we have studied the formation and nature of the solitary structure, electrostatic double layers (DLs), and so on. As we have considered weak relativistic degeneracy, only electrons get accelerated and are the key to stationary structures. We have implemented Sagdeev’s pseudopotential method, standard Gardner equation, and accordingly identified regimes where the solitary formation and DLs may be observed. We have studied the parametric influences on solitons and DLs. Furthermore, we extended our investigation to the oscillatory Rossby solitons in the ionospheric plasma. The results may help interpret many high-energy atmospheric observations in the ionospheric plasma. [ABSTRACT FROM AUTHOR]

The conventional approach to elucidate the atomic structure of liquid and glass is to start with local structural units made of several atoms, and to use them as building blocks to form a global structure, the bottom-up approach. We propose to add an alternative top-down approach in which we start with a global high-temperature gas state and then apply interatomic potentials to all atoms at once. This causes collective density wave instability in all directions with the same wavelength. These two driving forces, local and global, are in competition and are mutually frustrated. The final structure is determined through the compromise of frustration between these two, which creates the medium-range-order. This even-handed approach on global and local potential energy landscapes explains the distinct natures of short-range order and medium-range order, and strong temperature dependence of various properties of liquid.

The structure property is the fundamental factor in determining the stability, adsorption, catalytic performance, and selectivity of microporous materials. Seven density functional approximations (DFAs) are used to simulate the crystal structure of microporous material for examining the efficiency and accuracy. In comparison with the existing zeolites, microporous materials with CHA framework are selected as the testing model. The calculation results indicate that the least lattice volume deviation is 5.18/2.72 Å3 from PBE_mGGA, and the second least is −5.55/−10.36 Å3 from LDA_PP. Contrary to USPP_LDA, PBE_GW, PAW_PBE, and PAW_GGA overestimate the lattice volume by ~15.00–20.00 Å3. For each method, RMS deviations are less than 0.016 Å for bond length and less than 2.813° for bond angle. To complete the crystal structure calculation, the CPU time reduces in order of USPP_GGA > PBE_GW > PAW_GGA, PBE_mGGA > PAW_PBE > LDA_PP > USPP_LDA. For two testing models, when the calculation time is not important, PBE_mGGA is the best choice, and when the tradeoff between accuracy and efficiency is considered, LDA_PP is preferred. It seems feasible and efficient to simulate the zeolite structure through E-V curve fitting, full optimization, and phonon analysis bythe periodic density functional theory.

In the present article, the electrical and dynamical properties of C u 1 − X G a X binary alloys, viz., electrical resistivity, thermoelectric power, thermal conductivity, electron dispersion curve, phonon density of states, phonon dispersion curve and their related properties, are reported theoretically by using pseudopotential method for the first time. The screening influences are observed by adopting different exchange and correlation functions from the aforementioned properties. The present results of electrical resistivity are found in qualitative nature with available experimental data. [ABSTRACT FROM AUTHOR]

Based on the calculations from the first principles, we obtained the distributions of valence electron densities and electronic energy spectra for small Ptn clusters (where n = 1-5 atoms). According to the results of calculations, it is determined that the inclusion of oxygen atoms or atoms of other kinds in small Ptn clusters, as a rule, affect the catalytic activity of research systems. It is established that during doping of small platinum clusters by atoms of 3-d transition metals (Cu, Ni, Co), the electronic structure of the cluster and the band gap change. This in turn helps to increase the catalytic activity of platinum.

We investigate the low-energy scattering properties of two identical particles interacting via the polarized quadrupolar interaction. It is shown that a series of s - and p -wave resonances appear for identical bosons and fermions, respectively, as the strength of the quadrupolar interaction increases. Interestingly, scattering resonances also appear on the generalized scattering length corresponding to the coupling between the s and d waves. This observation inspires us to propose a new pseudopotential for the quadrupolar interaction. We also explore the bound-state properties of two particles in both free space and harmonic traps.

The implementation of boundary conditions is among the most challenging parts of modeling fluid flow through channels and complex media. Here, we show that the existing methods to deal with liquid‐wall interactions using multicomponent Lattice Boltzmann are accurate when the wall is aligned with the main axes of the lattice but fail otherwise. To solve this problem, we extend a strategy previously developed for multiphase models. As an example, we study the coalescence of two droplets on a curved surface in two dimensions. The strategy proposed here is of special relevance for binary flows in complex geometries. [ABSTRACT FROM AUTHOR]

Properties of the ground state of the helium atom embedded in classical nonideal plasmas have been investigated within the framework of variational method. The background plasma is described by a pseudopotential which has been deduced from the sequential solution of Bogolyubov's hierarchy equations. An extensive trial wave function is employed in Rayleigh–Ritz variational principle to compute various quantities associated with the ground state of helium atom quite accurately. A detailed study is made on the changes in those quantities introduced by the varying nonideality of the plasma in a wide range. In particular, special emphasis is made to study the stability of the atom in the plasma by computing the critical values of screening parameter and nonideal parameter accurately. To the best of our knowledge, such a study on the stability of helium atom in classical nonideal plasmas is reported for the first time in the literature. [ABSTRACT FROM AUTHOR]

The study of lattice mechanical properties of transition metals using pseudopotential is burdensome as the presence of d-band in these metals complicates their electronic structure. The use of pseudopotential for the study of physical properties can be justified if it accounts for the effect of d-band. The local form of the pseudopotentials is widely used to study the physical properties of materials due to their computational simplicity, physical transparency, and transferability to other environments. It is a well-established fact that non-local pseudopotentials should be preferred to the local ones. But, non-local pseudopotentials are proven to be at a higher computational cost. Inspired by such requirements, we, in the present communication, propose a pseudopotential comprising of one non-local (energy-dependent) and another local term in q-space. The non-local (energy-dependent) term accounts for s-p interaction, while the other term is used to account for the effect of s-d hybridisation. The Generalized Pseudopotential Theory (GPT) has been used to formulate the pseudopotential. Further, the pseudopotential has been used to study static binding energy, lattice dynamics, lattice mechanical properties and second-order elastic constants in the long-wavelength limit (q→0) for transition metals γ-Fe (fcc), Co and α-Fe (bcc). Computed results are found to be in good agreement with experimental and other theoretical results, which proves that the proposed pseudopotential itself accounts for the effect of d-band without using additional short-ranged Born–Mayer type potential and effective valency. [ABSTRACT FROM AUTHOR]

Parameters of the Ashcroft and Heine–Abarenkov model potential have been computed for face-centred cubic (fcc) actinium (Ac) crystal. The calculation uses the pseudopotential technique with nine different exchange and correlation functions and an empirical relation based on other experimental parameters, namely, the melting temperature and the cohesive energy. The complete set of values for this parameter will be used for future calculations of self-diffusion and impurity diffusion via a vacancy mechanism or via other types of defects. [ABSTRACT FROM AUTHOR]

In this paper, the structural parameters, energy bands structure, density ofstates and charge density of HgSe in the Zincblende(B3) phase have been investigated.The calculations have been performed using the Pseudopotential method in theframework of density functional theory (DFT) by Quantum Espresso package. Theresults for the electronic density of states (DOS) show that the band gap for HgSe iszero. The obtained energy bands structure for HgSe show that the lowest conductionband minimum and the top of the valence band are degenerate at the center of Brillouinzone (Г),and this compound is a zero-gap material or semimetal. Calculation of electroncharge density in zincblende phase in (110) plane show that this compound has ionicand covalent bond simultaneously. The theoretical calculated optical properties andenergy Loss (EEL) spectrum yield a static refractive index of4.37and a plasmon energyof 22.83eV for cubic phase. This calculation are in good agreement with the othertheoretical and experimental values.

Quantum mechanical calculations have been accomplished to study the dynamics of the reaction: p + H(1s) → H(nlm) + p in dense semi‐classical hydrogen plasma. Interactions among the charged particles in plasma are represented by a pseudopotential which takes care of the collective effects at large distances and quantum effect of diffraction at small distances. Various capture cross sections are computed for the incident proton energy lying within 10 to 500 keV by applying a distorted wave method which uses a variationally determined closed‐form wave function of hydrogen atom. Moreover, an inclusive study is made to explore the effects of screening of plasma and quantum diffraction on various capture cross sections for a wide range of thermal Debye length and de Broglie wave length. It has been found that various cross sections suffer considerable changes due to varying Debye length and de Broglie wave length. [ABSTRACT FROM AUTHOR]

Ab initio calculations were performed to investigate the structural and electronic properties of bulk CdTe using various exchange–correlation (XC) functionals available. Among the selected XC functionals include the local density approximation (LDA), generalized gradient approximation (GGA), meta-generalized gradient approximation (MGGA) (using the linear combination of atomic orbitals basis scheme) and Heyd–Scuseria–Ernzerhof-06 (HSE06) (using the plane-wave basis scheme). Further computational studies were performed based on the local density approximation-1/2 (LDA-1/2) and generalized gradient approximation-1/2 (GGA-1/2) self-energy correction schemes to verify their effect on the CdTe band gap in comparison to the other traditional XC functionals. The lattice parameter values obtained using different XC functionals (LDA, GGA and MGGA) were well in agreement with experimental value, with LDA predicting 6.548 Å. This is 1.02% greater than the experimental value of 6.482 Å. The electronic structure of CdTe was calculated for the fixed 6.482 Å lattice parameter of bulk CdTe and resulted in a band gap ranging between 0.68 and 1.56 eV for LDA, GGA, MGGA, and HSE06. The band gap values predicted by the LDA-1/2 and GGA-1/2 corrections were 1.47 eV and 1.50 eV, respectively, and are found to be in good agreement with experimental values. The influence of XC functionals and semi-empirical correction schemes are expected to have important implications on the prediction and understanding of bulk CdTe thin-films found in photovoltaic applications. [ABSTRACT FROM AUTHOR]

Non-uniform height semiconductor quantum rings are studied in order to determine their electronic and optical absorption properties. Theoretical modelling of the structure includes an analytical description of the non-regular multi-hilled confining potential as well as the presence of repulsive scattering centre and external crossing electric and magnetic fields. We have discussed the features of localised and extended (rotational, Aharonov–Bohm-like) states in the presence of the magnetic field. A modification of the spectrum, with the appearance of a Stark-like behaviour, and its corresponding modification related to the repulsive potential is analysed when the electric field effect is considered. In double-hilled structures, these properties of the energy spectrum are of main importance in explaining the apparent optical transparency induced within a certain range of the electric field strength. The presence of the repulsive centre is found to cause a moderate redshift of the light absorption response. [ABSTRACT FROM AUTHOR]

In this paper, we account the electrical transport properties of Bi-Ga alloys studied theoretically by employing our well-known model pseudopotential. The impact of various screening functions was studied using various exchange and correlation functions in the aforesaid investigation. The obtained results on electrical resistivity are found to be in qualitative agreement with the experimental data in available literature.

Effects of nonideality of classical plasma on the reaction: p + H(1s) → H(nlm) + p has been investigated by carrying out fully quantum mechanical calculations within the framework of a first‐order distorted wave method. Scattering amplitude is calculated conveniently by employing a simple, variationally determined wave function of hydrogen atom embedded in nonideal classical plasma. A detailed study is made on the changes in electron transfer cross sections due to the nonideality of plasma varying from 0 to 4 and the incident proton energy lying between 10 and 500 keV. It has been found that nonideality of plasma causes substantial change in capture cross section. [ABSTRACT FROM AUTHOR]

• Eelectromagnetic solitary waves can propagate as compressive or rarefactive type solitons. • The electromagnetic solitons exist symmetrically for the wave magnetic field. • Both the sub-Alfvénic and super-Alfvénic solitons exist in the weakly relativistic regime. • Only sub-Alfvénic solitons exist in the ultrarelativistic regime. Nonlinear propagation of purely stationary large amplitude electromagnetic (EM) solitary waves in a magnetized electron–positron (EP) plasma is studied using a fully relativistic two-fluid hydrodynamic model which accounts for physical regimes of both weakly relativistic (P ≪ nmc 2) and ultrarelativistic (P ≫ nmc 2) random thermal energies. Here, P is the thermal pressure, n the number density and m the mass of a particle, and c is the speed of light in vacuum. While both the sub-Alfvénic and super-Alfvénic solitons coexist in the weakly relativistic regime, the ultrarelativistic EP plasmas in contrast support only the sub-Alfvénic solitons. Different limits of the Mach numbers and soliton amplitudes are also examined in these two physical regimes. [ABSTRACT FROM AUTHOR]

In the present paper, we report the electrical transport properties, namely electrical resistivity, thermoelectric power and thermal conductivity by using Shaw's constant core model pseudopotential in conjunction with Ziman's theory of electrical properties of some 20 bulk metallic glasses constituted by binary to hexanary metallic elements for the first time. The screening influences are studied by different exchange and correlation functions. The current fallouts of electrical resistivity are observed in qualitative nature with available experimental data. [ABSTRACT FROM AUTHOR]

Accurate assessment of electrical transport for heavy polyvalent metals pause challenge due to complex electronic band structure, where s-wave scattering theory due to Ziman is failed. Improving schemes like t-matrix resistivity and self-consistent approach are proposed. In the present study, we employ selfconsistent approach to compute electrical resistivity (ρ) in liquid Bi and Sb at different temperatures (T). Structural input is estimated through charged hard-sphere reference system. Electron-ion interaction is modelled by modified empty-core pseudopotential including electron exchange and correlation effects. Since only two parameters are independent, as the core radius RC (= 0.51 RaZ-1/3) is a theoretical input, we have tuned, once and for all, the single parameter to find ρ at melting temperature. The same set of parameters is used to deduce high-T resistivity, thermal conductivity and thermo-electric power. Overall good agreement is observed for transport properties for both metals. The present fitting scheme and so deduced results are discussed in comparison with other findings. [ABSTRACT FROM AUTHOR]

Pseudopotential methods have been used successfully to understand static, dynamical and transport properties with good degree of agreement in condensed matter physics. In the present communication, we have investigated lattice dynamics of Ca and Sr in bcc phase using local pseudopotential due to George et al. The pseudopotential contains two parameters rc and β which are determined from zero pressure condition. The computed results of phonon frequencies are in good agreement with experimental finding and maximum deviation for both the metals are about 10 % with experimental findings. Further, we have computed dynamical elastic constants (C11, C12 and C44) and bulk moduli (B) which are also comparable with experimental results and other theoretical results. Success of present study reveals that both metals behave as a simple metal rather than early transition metals and extra term for the inclusion of s-d hybridization is not required. [ABSTRACT FROM AUTHOR]

The pseudopotential-based formulation suggested by MacMillan utilized for computing the five most important superconducting state parameters (SSPs) given by electron–phonon coupling strength λ, Coulomb pseudopotential μ∗, transition temperature TC, isotope effect exponent α, and effective interaction strength NOV of 20 bulk metallic glasses (BMGs) having the range of binary to hexanary combinations made from simple and non-simple metallic elements for the first time are reported in the present study. Shaw's constant core pseudopotential with five different types of local field functions given by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F), and Sarkar et al. (S) are used in the present calculation for seeing the screening impacts on the abovementioned parameters. It is also observed from the present study that two parameters λ and TC are shown quite sensitive to the local field functions in contrast with the other three parameters. Also, the present outcomes support the superconducting nature in the considered BMG systems. [ABSTRACT FROM AUTHOR]

The adiabatic potential energy curves for ground and many excited states of 1, 3Σ+, 1,3Π, 1,3Δ symmetries of the LiNa molecule have been performed. We have used an ab initio approach based on non-empirical pseudopotentials, parameterised l-dependent polarisation potentials and full configuration interaction calculations. In addition, the adiabatic potential energy curves determined in our previous work [Mabrouk and Berriche, J. Phys. B: At. Mol. Opt. Phys. 41, 155101 (2008).] are corrected by using a diabatisation procedure, based on the effective Hamiltonian theory and an effective metric. The diabatic permanent moments for first 10 1Σ+ electronic states show linear behaviours, especially at intermediate and large distance. The transition dipole moment between neighbour states has revealed many peaks located around the avoided crossing positions. The radial coupling between the adiabatic states was calculated using the Hellmann-Feynman formula and numerical differentiation of the rotation matrix. The first and the second derivatives revealed many peaks, associated to neutral-neutral and ionic-neutral crossings. Furthermore, the radial coupling is used to evaluate the adiabatic correction, which is found to be of an order of tens and hundreds of cm−1, especially of higher excited states. In addition, we have determined the vibrational level spacing for all studied states. [ABSTRACT FROM AUTHOR]

Single vibrational scaling factors for the calculation of enthalpies of formation at a given level of theory are widely used and statistically correct. However, it can be shown that for several molecules the error is substantial, and it is possible to determine selective molecular scaling factors that minimize or eliminate the deviation between theoretical enthalpies of formation with respect to accurate experimental data. Selective scaling factors for 248 enthalpies of formation relative to the experimental data using the G3(MP2)//B3-CEP composite method reduced the mean absolute error from 1.55 to 0.64 kcal mol−1. This error is smaller than the mean absolute error of some of the most sophisticated methods from the Gn family and other composite methods. The similarity among scaling parameters for molecules with comparable characteristics indicates that the optimum parameters are not a random empirical adjustment but must be related to the nature of the chemical bonds, the atomic species, and possibly the level of theory used. Molecules with the same functional groups and similar types of bonds presented similar vibrational scaling factors. [ABSTRACT FROM AUTHOR]