Structural and electronic properties of molten GaAs

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Abstract
The authors present the first microscopic investigation of the atomic and electronic structure of a molten-compound semiconductor. Their approach is based on pseudopotential-derived interatomic forces, a molecular-dynamic simulation of the atomic structure, and a supercell linearised-muffin-tin-orbital calculation of the electronic density of states. Results for the atomic structure of molten GaAs are in good agreement with recent neutron-diffraction data. They find that the complex structure of the metallic melt arises from the modulation of the random packing of the atoms by the Friedel modulations in the effective interatomic interactions. The arrangement of the atoms is chemically random and shows only weak angular correlations. This has important consequences for the electronic structure. The loss of bond-orientational order on melting leads to the disappearance of the optical covalent gap and to the semiconductor-metal transition. The large number of like-atom ('wrong') bonds causes the filling of the ionic gap characteristic of the compound semiconductors. The s bands of both As and Ga are broadened so that the As s band is no longer separated from the rest of the valence band.