On the bases of the Percus-Yevick (PY) hard sphere model as a reference system and the Gibbs–Bogoliubov (GB) inequality, a thermodynamic perturbation method has been applied with use of well known model potential. By applying a variational method the best hard core diameters have been found which correspond to minimum free energy. With this procedure the thermodynamical properties such as internal energy, entropy, Helmholtz free energy, entropy of mixing and heat of mixing have been computed for liquid NaK binary systems. The influence of local field correction function viz; Hartree (HR), Taylor (TY), Ichimaru-Utsumi (IU), Farid et al. (FD) and Sarkar et al. (SS) is also investigated. The computed excess entropy compares favourably in the case of liquid alloys while the agreement with the experiment is poor in the case of heats of mixing. This may be due to the sensitivity of the heats of mixing, with the potential parameters and the dielectric function.

In this paper, structural parameters such as lattice constants, bulk modulus, derivative of bulk modulus, also phonon properties and density of phonon states of LaLi3Sb2 composition with trigonal crystal structure (space group p31m) have been discussed. The calculations have been done in the framework of the density functional theory and with the Pseudopotential method in the Local Density Approximation (LDA) by the Quantum Espresso Software. The value of the bulk modulus, obtained in the LDA approximation is equal B= 49 GPA. The phonon spectrum of LaLi3Sb2 composition shows that 50% of the branches are located in the frequency range of 0-140 cm-1, which includes both optical and acoustic modes, and there is not any frequency gap observed in this range. At higher frequencies, only optical mode and frequency gap were observed. The examination of the phonon density of states showed that the heavy atoms, La and Sb only play a role in low frequencies and have no effect in high frequencies, where only the optical mode were observed, but Li atom plays a significant role in all frequencies, especially high frequencies.

In this paper the electronic, structure and optical properties of strontium sulfide in rocksalt phase have been studied. The calculation have been performed using Pseudopotential method in the framework of density functional theory (DFT) by Abinit package. in this calculation we used of localized density approximation (LDA) and generaliezed geradient (GGA) approximation. The obtained result have been good agreement with other theory and experimental results.

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 show that the crown shape is related to 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 potential of being used for multiphase problems with large density ratios while producing a low spurious current could be utilized for a wide variety of other multiphase problems as well.

Plane-wave Pseudopotential Density Functional Theory (DFT) periodic slab calculations were performed using the generalized gradient approximation (GGA) to investigate the adsorption of nitric oxide (NO) on the (111) surface of Cu. Copper surface was simulated using the Periodic Slab Method consisting of five atomic layers.Four different adsorption sites (Atop, Bridge, HCP Hollow, and FCC Hollow) were considered. Results specified that the suitable site for NO adsorption in molecular form is the Hollow FCC site, and molecular adsorption is more stable than dissociative adsorption energetically.

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.

In this paper, we have calculated the InAs structural parameters such as lattice constant, bulk modulus and its derivative, stability and density state in zincblende and wurtzite phases. The calculations have been performed using Pseudopotential method in the framework of density functional theory by Espresso package. The calculated structural parameters are in good agreement with experimental results. The results showed that zincblende phase is more stable than wurtzite phase and InAs in zincblende and wurtzite phases is a narrow gap semiconductor. Also, the results of the contribution of different orbitals show that in the conduction band, there is a strong overlap between p orbitals of In and As atoms and the orbital s of In, while at the top of the valence band, the overlap of p orbitals of In and As atoms is predominant.

In the present paper, the phonon dispersion curves (PDC) of some equiatomic liquid alkali binary alloys are reported in second order approach through the equation given by Hubbard and Beeby (HB). The pair correlation function g (r) is directly computed from the interatomic pair potential, which is used in the present computation. Two different forms of local field correction functions proposed by Hartree (H) and Ichimaru-Utsumi (IU) are used in the present study the screening dependence of the phonon frequencies in the equiatomic liquid alkali binary alloys. The pseudo-alloy-atom (PAA) model is applied for the first time for the alloying elements.

In this study, the structural, electronic, and optical properties of strontium chalcogenides are investigated by the Pseudopotential method in the framework of density functional theory and quantum espresso code. The calculations were performed with the LDA, GGA, and HSE approximations. The calculated structural parameters are in good agreement with available experimental and theoretical data. The results of the band structure show that these compounds in B1 phase are semiconductors with an indirect band gap. The band gap calculated for compounds in B1 phase in the LDA and GGA approximations is consistent with the theoretical data of others. Also, the band gap in HSE approximation for SrS, SrSe, and SrTe compounds were calculated 4. 30, 3. 86, and 2. 96 eV, respectively, which is in agreement with the experimental data. The dielectric constant for SrS, SrSe, and SrTe compounds was calculated as 4. 73, 5. 02, and 5. 86 in GGA and 5. 27, 5. 48, and 6. 50 in the LDA approximation, respectively and these results are also consistent with available experimental and theoretical data.

Propagation of ion acoustic solitary waves (IASWs) in electronegative plasma containing positive and negative ions, trapped and non-thermal electrons are investigated. Using the Sagdeev Pseudopotential method and investigation of the energy integral, the existence of propagation regions for these waves is analyzed. It is shown that the Mach number, positive and negative ions densities ratio and the trapping parameter can lead to change the Pseudopotential amplitude and also it is shown that the lower limit of the Mach number increases with the density and mass ratios of positive and negative ions, but the upper limit of the Mach number does not depend on the densities ratio. The results show that for this kind plasma, there is only compressive IASW. This research will be helpful in understanding of physical phenomena concerned in plasmas in which the effects of trapped electrons control the dynamics of wave.