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Truncated methods applied to the direct calculation of exciton binding energies

AuthorsLeonardo, Aritz; Arruabarrena, Mikel; Bergara, Aitor ; Ayuela, Andrés
Issue Date4-Mar-2019
CitationAPS March Meeting (2019)
AbstractOptical processes in insulators and semiconductors, including excitonic effects, can be described in principle exactly using time-dependent density-functional theory (TDDFT). Within this formalism, a family of exchange-correlation kernels known as long-range-corrected (LRC) kernels (fxc=-α/q2) have shown to accurately reproduce optical spectra for several insulators and semiconductors. More recently, Ullrich and co-workers adapted the Casida equation formalism suitable for determining molecular excitations to periodic solids, this way the exciton binding energy may be calculated in a direct way without having to compute explicitly the response function. However, it appears that no LRC-type kernel is capable of simultaneously produce good optical spectra and quantitatively accurate exciton binding energies. In the present work we have adapted Casida's formalism following a different approach. The long range nature of the kernel, i.e. the q->0 singularity, is regularized employing a super-cell wigner-seitz truncation that clearly alters the previously calculated alpha values of the kernel. We will justify our calculation method and provide the alpha values for several insulating/semi-conducting materials.
DescriptionTrabajo presentado en APS (American Physical Society) March Meeting, celebrado en Boston (Estados Unidos), del 4 al 8 de marzo de 2019
Appears in Collections:(CFM) Comunicaciones congresos
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