Quantum Monte Carlo calculations in solids with downfolded Hamiltonians
Abstract
We present a systematic downfolding many-body approach for extended systems. Many-body calculations operate on a simpler Hamiltonian which retains material-specific properties. The Hamiltonian is systematically improvable and allows one to dial, in principle, between the simplest model and the original Hamiltonian. As a by-product, pseudopotential errors are essentially eliminated using a frozen-core treatment. The computational cost of the many-body calculation is dramatically reduced without sacrificing accuracy. We use the auxiliary-field quantum Monte Carlo (AFQMC) method to solve the downfolded Hamiltonian. Excellent accuracy is achieved for a range of solids, including semiconductors, ionic insulators, and metals. We further test the method by determining the spin gap in NiO, a challenging prototypical material with strong electron correlation effects. This approach greatly extends the reach of general, ab initio many-body calculations in materials.
Cite
@article{arxiv.1412.0322,
title = {Quantum Monte Carlo calculations in solids with downfolded Hamiltonians},
author = {Fengjie Ma and Wirawan Purwanto and Shiwei Zhang and Henry Krakauer},
journal= {arXiv preprint arXiv:1412.0322},
year = {2015}
}