Ab initio static atomistic simulations including semiempirical polarization energy corrections are performed to investigate the stability under pressure of cubic $(B1\mathrm{}$ and $B2)$ and orthorhombic $\mathrm{}\left(B33\mathrm{}\right)\mathrm{}$ structures of NaBr, NaI, and LiBr crystals. The calculated unit-cell geometries, equations of state parameters, and phase-transition properties show systematic trends controlled by the ionic sizes and compare successfully with available experimental data. A microscopic analysis of the crystal energy identifies the anionic polarization contribution as essential to explain: (i) the preference of the recently observed $B\overrightarrow{1}B33\mathrm{}$ transformation over the $B\overrightarrow{1}B2\mathrm{}$ one in NaBr and NaI and (ii) the potential appearance of the orthorhombic phase at high pressures in lithium halide crystals.

• Received 27 March 2003

DOI:https://doi.org/10.1103/PhysRevB.68.014110