Ab initiotheory of polar semiconductor surfaces. II. (22) reconstructions and related phase transitions of GaAs(1¯1¯1¯)

The (2×{}2) reconstructions of GaAs(1{} 1{} 1{}) are studied with use of a theoretical approach based on the calculation of the total energy in the context of density-functional theory and the pseudopotential approximation. New models are proposed for the As-rich and Ga-rich reconstructions. The relative chemical potential plays a crucial role in determining the lowest-energy configuration. The total-energy versus chemical-potential curves indicate the possibility of phase transitions between different configurations. One such transition concerning the experimentally observed ({}19 ×{} {}19 ) reconstruction can be explained as an intermediate phase between the proposed low-energy (2×{}2) reconstructions.