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Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 98: Electronic Structure Theory

HL 98.4: Talk

Friday, March 30, 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 Nieminen11Aalto 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.

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