Direct calculations of charge densities of solids: Applications to the alkali‐earth sulfides

Abstract

mWe performed ab initio self-consistent calculations for the five alkali-earth sulfides-BeS, MgS, CaS, SrS, and Bas-by a method which allows the direct calculation of the ground-state electron density without a preliminar determination of the wave functions and of the energy eigenvalues of the system. We report the results for the standard cohesive properties (equilibrium lattice parameters, dissociation energies, bulk moduli), a study of the relative stability of the B1 (NaCl), B2 (CsCl), and B3 (ZnS) phases, and of the behavior under pressure of these compounds (equation of state; pressure and change of volume associated to the structural phase transition 81 + B2 or B3 + Bl).

Ab‐initio study of the structural phase transition of SrSe and SrTe under pressure

“…The results that we have obtained for the lattice parameters, the binding energies, and the bulk moduli are reported in Tables I–III, respectively. In the same Tables are also reported the values obtained by the same method for SrO 24 and SrS 23. It appears that the errors on the calculated lattice parameters never exceed 1.5%, the theoretical values being systematically smaller than the experimental ones, according to a general trend of results obtained by means of DFT ab initio calculations.…”

“…Some years ago, the author has proposed a method allowing the direct determination of the total energy and the electron density of a system 19. The method has been applied in order to study ionic 20–25 as well as metallic solids 26 and to a variety of problems, including solvation 27, adsorption on surfaces 28, and stability of weak van der Waals complexes 29.…”

Theoretical study of the phonon properties of SrS

“…SrS has been found to undergo a first-order phase transition from the B1 structure to the B2 structure at 18 GPa, as shown by X-ray diffraction experiments [4]. In addition, considerable progress has been made in the theoretical description of its structural phase transformation under pressure, its electronic, optical, and elastic properties, and the volume dependence of energy gap of SrS [5][6][7][8][9][10][11][12][13][14][15][16]. Phonon properties of solids are important because they are closely associated with various fundamental solid-state properties, such as thermal expansion, specific heat, electron-phonon interaction, heat conduction, and thermal conduction of the lattice.…”

A flexible implementation of frozen‐density embedding for use in multilevel simulations

“…By construction, it scales linearly with the number of subsystems. Initially, it has been applied by Cortona et al for calculations on simple ionic crystals (e.g., alkali halides,33 alkali‐earth oxides,34 and alkali‐earth sulfides35), by determining the densities of the ions individually. While in the implementation of Cortona, these densities are constraint to be spherical, an extended scheme has been implemented by Mehl and coworkers.…”