Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 44: Poster II

HL 44.71: Poster

Thursday, March 11, 2004, 16:30–19:00, Poster A

Ab-initio investigation of the high-pressure phase transition cd→β-tin under nonhydrostatic pressure in Si and Ge — •Katalin Gaál-Nagy and Dieter Strauch — Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg

In this contribution we present an ab-initio study of the high-pressure phase transition from the cubic-diamond (cd) to the β-tin phase in Si and Ge. Our main interest is here the influence of non-hydrostatic pressure to the transition. In a first step we calculated the full curve of the equation of state from a enthalpy surface including energies and enthalpies for the complete set of parameters which are allowed to vary. This the H(p) curve is calculated by evaluating the hydrostatic pressure concerning the components of the diagonal stress tensor beeing equal. Next a similar procedure can be done for non-equal components for non-hydrostatic pressure. Last we included the effect of strain in our calculations. We find an essentual lowering of the transition pressure under non-hydrostatic conditions. The calculations were performed within the framework of the density functional theory using ultrasoft pseudopotentials and the local density as well as the generalized gradient approximation for the exchange-correlation potential implemented in VASP [1].

[1] G. Kresse, J. Furthmüller, Comput. Mat. Scie. 6, 15 (1996)