Compared electron charge densities for the series of solid phosphide compounds; anab initiostudy

Abstract

The wave functions of boron, aluminium and gallium phosphides have been calculated at both the Hartree - Fock and local density approximation levels using the ab initio linear combination of atomic orbitals method implemented in the program CRYSTAL. The Mulliken populations, bandstructure, electron charge densities, and structure factors are evaluated and compared. The chemical bonds are mainly covalent, as revealed by the difference electron charge-density maps obtained by subtracting from the total densities the superposition of the spherical atomic densities. A charge-density accumulation between the nearest neighbours slightly shifted towards the phosphorus appears in the AlP and GaP compounds, whereas an opposite charge transfer from phosphorus to boron is observed in boron phosphide from the Mulliken population analysis.

Competition between the ionic and covalent character in the series of boron compounds BP, BAs, and BSb

“…Similar conclusions have been established from other ab initio calculations [8]. These results also confirm the theoretical analysis of Lichanot and Causà [29] using an ab initio LCAO method which shows a significant electron charge transfer from P to B in BP.…”

“…From the best fit of the total energies, we also calculated the values of the bulk moduli to be 1.72 Mbar, 1.44 Mbar, and 1.08 Mbar, and their pressure derivatives to be 3.76, 4.00 and 4.03, for BP, BAs, and BSb, respectively. Table 4 reports the equilibrium data calculated at the LDA level and compares them with those obtained at the LDA level using a plane-wave basis set (for BP and BAs, references [8,9]), those previously obtained at the HF level using an allelectron basis set (for BP, reference [28]), and at the LDA level using a linear combination of atomic orbitals (LCAO) scheme (for BP, reference [29]). Our predicted values for B 0 agree with those determined by using the empirical formula of Cohen [30] which seems to be valid for the series of boron compounds.…”

Pressure-induced structural phase transition and electronic structure ofIn1

“…In the literature, the structural data for the starting (at x = 0.0) compound InP and the end (at x = 1) compound GaP are available for comparison. The calculated optimized structural parameters are in good agreement with other available theoretical and experimental data [21][22][23][24][25][26][27][28][29][30][31][32], as given in Table 1.…”

Trends in band-gap pressure coefficients in boron compounds BP, BAs, and BSb

“…From these fits, we also calculated the values of the bulk moduli to be 1.72 Mbar, 1.44 Mbar, and 1.08 Mbar, and their pressure derivatives to be 3.76, 4.00, and 4.03, for BP, BAs, and BSb, respectively. In table 1 we summarize our data at equilibrium and compare them with those obtained from other calculations at the LDA level using a plane-wave basis set (for BP and BAs; references [8,9]), those previously obtained at the Hartree-Fock (HF) level using an all-electron basis set (for BP; reference [27]), and at the LDA level using a linear combination of atomic orbitals (LCAO) scheme (for BP; reference [28]). It is well known that the HF calculations overestimate the lattice parameters.…”