Stochastic Resolution of Identity for Real-Time Second-Order Green's Function: Ionization Potential and Quasi-particle Spectrum

2019/09/14 by Dou, Wenjie, Takeshita, Tyler Y., Chen, Ming +3 · 2 citations
#Chemical Physics (physics.chem-ph) #FOS: Physical sciences

paper · doi:10.48550/arxiv.1909.06525

Abstract

We develop a stochastic resolution of identity approach to the real-time second-order Green's function (real-time sRI-GF2) theory, extending our recent work for imaginary-time Matsubara Green's function \em J. Chem. Phys. \bf 151, 044114 (2019)). The approach provides a framework to obtain the quasi-particle spectra across a wide range of frequencies as well as predict ionization potentials and electron affinities. To assess the accuracy of the real-time sRI-GF2, we study a series of molecules and compare our results to experiments and to a many-body perturbation approach based on the GW approximation, where we find that the real-time sRI-GF2 is as accurate as self-consistent GW. The stochastic formulation reduces the formal scaling to O(N_e³), where N_e is the number of electrons. This is illustrated for a chain of hydrogen dimers, where we observe a slightly lower than cubic scaling for systems containing up to N_e ≈ 1000.

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• Noise-reduced stochastic resolution of identity to CC2 for large-scale calculations via tensor hypercontraction
• Stochastic resolution of identity to CC2 for large systems: Excited-state gradients and derivative couplings

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