Article

Solids under Pressure. Ab Initio Theory

physica status solidi (b) (Impact Factor: 1.61). 09/1998; 211(1). DOI: 10.1002/(SICI)1521-3951(199901)211:1<5::AID-PSSB5>3.0.CO;2-N
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ABSTRACT Parameter-free calculations based on the density-functional theory are used to examine high-pressure phases of solids, mainly semiconductors. For the elemental semiconductors, as represented by Si, the diamond!fi-tin!Imma sequence is examined, and for III-V semiconductors the optimization of the structural parameters of the Cmcm and Imm2 phases is described. The structural energy differences are in several cases very small, and in some too small to allow a safe structure prediction on the basis of the calculations. In that context we also discuss ways to go beyond the local density approximation (LDA). We show that the predicted high-pressure phases may be significantly affected by inclusion of (generalized) gradient corrections (GGA). Elemental Zn (hcp) is further taken as an example where we find that the simple LDA leads to poor results. 1 I. INTRODUCTION Theoretical studies of cohesive, structural and vibrational properties of semiconductors under pressure are now routinely bein...

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    ABSTRACT: Parameter-free calculations based on the density-functional theory are used to examine high-pressure phases of solids. For the elemental semiconductors, as represented by Si, the high-pressure phases are examined in some detail, and particular attention is paid to the Si(VI)orthorhombic (Cmca) structure which was resolved only very recently. For III–V semiconductors the optimization of the structural parameters of the Cmcm and Imm2 phases is described. The structural energy differences are in several cases very small, and in some cases too small to allow a safe structure prediction on the basis of the calculations. In that context we also discuss ways to go beyond the local density approximation (LDA). We show that the predicted high-pressure phases may be significantly affected by inclusion of (generalized) gradient corrections (GGA). Elemental Zn (hcp) is further taken as an example where we find that the simple LDA leads to poor results for the equilibrium volume and axial ratio (c/a). Introducing corrections, for example by GGA, it is, however, possible to achieve an accuracy that allows a study of the structural changes of Zn (and Cd) under pressure and analysis of these changes in terms of electronic topological transitions. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 880–894, 2000
    International Journal of Quantum Chemistry 01/2000; 77(5):880 - 894. DOI:10.1002/(SICI)1097-461X(2000)77:5<880::AID-QUA9>3.0.CO;2-2 · 1.17 Impact Factor
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    01/2000; Springer-Verlag., ISBN: 3540649662
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    ABSTRACT: Pressure-driven transitions of ionic materials from the zinc-blende to rocksalt and δ-ZnCl2 to CdCl2 crystal structures are studied using constant-stress molecular dynamics with a polarizable-ion potential model. Both transformations are characterized by a change in cation coordination environment from tetrahedral to octahedral and are nonmartensitic. Transformation mechanisms are identified and characterized and similarities discussed. The blende to rocksalt transformation is observed to proceed via a diatomic β-tin-like structure, though this is shown to be a transition state and not a true intermediate phase in this system. The relationship of the observed mechanisms to those deduced from experiments on halide systems is discussed. The development of displacive motion across the simulation cell is discussed. The ZnCl2 system is a layered structure, and while the coordination changes are highly cooperative within each layer, the overall transformation takes place on a layer-by-layer basis. In the blende, the interlayer correlations required to produce a grain-boundary-free final structure are associated with a shearing motion which propagates across the cell. These differences have characteristic effects on the kinetics of the transformations.
    Physical Review B 02/2002; 65(9). DOI:10.1103/PhysRevB.65.094109 · 3.74 Impact Factor
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