paper

Gradient-based stochastic estimation of the density matrix

arXiv:1711.10570 · doi:10.1063/1.5017741

Abstract

Fast estimation of the single-particle density matrix is key to many applications in quantum chemistry and condensed matter physics. The best numerical methods leverage the fact that the density matrix elements decay rapidly with distance between orbitals. This decay is usually exponential. However, for the special case of metals at zero temperature, algebraic decay of the density matrix appears and poses a significant numerical challenge. We introduce a gradient-based probing method to estimate all local density matrix elements at a computational cost that scales linearly with system size. For zero-temperature metals the stochastic error scales like , where is the dimension and is a prefactor to the computational cost. The convergence becomes exponential if the system is at finite temperature or is insulating.

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