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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Local ab initio methods for calculating optical bandgaps in periodic systems. II. Periodic density fitted local
Marco Lorenz1, Lorenzo Maschio, Martin Schütz
1Institute for Physical and Theoretical Chemistry, Universität Regensburg, Universitätsstrasse 31, D-93040 Regensburg, Germany.
Abstract:
We present a density fitted local configuration interaction singles (CIS) method for calculating optical bandgaps in 3D-periodic systems. We employ an Ewald technique to carry out infinite lattice summations for the exciton-exciton interaction, and robust product-density specific local density fitting in direct space for the electron-hole interaction. Moreover, we propose an alternative to the usual cyclic model with Born-von Karman periodic boundary conditions, the so called Wigner-Seitz supercell truncated infinite model, which exhibits much improved convergence of the CIS excitation energy with respect to the size of the supercell. Test calculations on a series of prototypical systems demonstrate that the method at the present stage can be used to calculate the excitonic bandgaps of 3D periodic systems with up to a dozen atoms in the unit cell, ranging from wide-gap insulators to semiconductors.
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