Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 98: Electronic Structure Theory
HL 98.4: Vortrag
Freitag, 30. März 2012, 10:15–10:30, EW 202
From long- to short-range correlations in the many-body perturbation theory — •Andris Gulans1, Torbjörn Björkman1, Natalia Berseneva1, Arkady Krasheninnikov1,2, and Risto Nieminen1 — 1Aalto University School of Science, Espoo, Finland — 2University of Helsinki, Finland
Exfoliated layered solids commonly exhibit unusual properties in comparison to their bulk counterparts. Reliable theoretical studies of these materials often require more than just the standard density functional theory. Then, it is desirable to apply methods of the many-body perturbation theory, but they converge slowly with respect to the basis size. We argue that this problem stems from the electron-electron interaction cusp of correlated wavefunctions. Our analysis of the uniform electron gas shows that RPA correlation energies as well as GW quasiparticle energies converge as the negative third power of the cut-off wavevector, and also a further asymptotic expansion is possible. This result is applied for a study of binding in 30 layered solids and the quasiparticle band structure of BN and MoS2. Obtained exfoliation energies are surprisingly similar with the typical value of 20 meV/Å2. The quasiparticle calculations show that the band gaps strongly depend on the width of the vacuum gap between periodic images of single layers, which is another long-range correlation effect along with the van der Waals interaction. The accuracy of these results is strongly influenced by the treatment of the short-range electron correlations.