Abstract |
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G0W0 corrections to DFT band structures are a popular way to go beyond the accuracy DFT is able to provide. However, the calculation of such corrections with the ABINIT code is currently prohibitive for systems with more than a few hundreds of electrons. What limits the calculations to this system size is the need in the current implementation to invert the dielectric matrix and to carry out some summation over conduction bands. This poster presents a strategy to avoid both of these limitations for the screened-exchange contribution to the self-energy. In ABINIT’s implementation, the dielectric matrix is expressed in a plane wave basis, which needs to be relatively big to properly describe the matrix. This poster explains how a Lanczos basis can be generated to substantially reduce the size of the matrix. Also, the number of conduction bands needed to reach convergence in the summation is usually an order of magnitude bigger than the number of valence bands. Here, the calculation of all the conduction states is avoided by reformulating the summation into a linear equation problem (Sternheimer equation), which also substantially reduces the computation time. |