Abstract
We review recent advances in the capabilities of the open source ab initio Quantum Monte Carlo (QMC) package QMCPACK and the workflow tool Nexus used for greater efficiency and reproducibility. The auxiliary field QMC (AFQMC) implementation has been greatly expanded to include k-point symmetries, tensor-hypercontraction, and accelerated graphical processing unit (GPU) support. These scaling and memory reductions greatly increase the number of orbitals that can practically be included in AFQMC calculations, increasing the accuracy. Advances in real space methods include techniques for accurate computation of bandgaps and for systematically improving the nodal surface of ground state wavefunctions. Results of these calculations can be used to validate application of more approximate electronic structure methods, including GW and density functional based techniques. To provide an improved foundation for these calculations, we utilize a new set of correlation-consistent effective core potentials (pseudopotentials) that are more accurate than previous sets; these can also be applied in quantum-chemical and other many-body applications, not only QMC. These advances increase the efficiency, accuracy, and range of properties that can be studied in both molecules and materials with QMC and QMCPACK.
Highlights
Quantum Monte Carlo (QMC) methods are an attractive approach for accurately computing and analyzing solutions of the Schrödinger equation.1–3 The methods form a general ab initio methodology able to solve the quantum many-body problem, applicable to idealized models such as chains or lattices of atoms to complex and low-symmetry molecular and condensed matter systems, whether finite or periodic, metallic or insulating, and with weak to strong electronic correlations
We review recent advances in the capabilities of the open source ab initio Quantum Monte Carlo (QMC) package QMCPACK and the workflow tool Nexus used for greater efficiency and reproducibility
To provide an improved foundation for these calculations, we utilize a new set of correlation-consistent effective core potentials that are more accurate than previous sets; these can scitation.org/journal/jcp be applied in quantum-chemical and other many-body applications, QMC
Summary
Quantum Monte Carlo (QMC) methods are an attractive approach for accurately computing and analyzing solutions of the Schrödinger equation. The methods form a general ab initio methodology able to solve the quantum many-body problem, applicable to idealized models such as chains or lattices of atoms to complex and low-symmetry molecular and condensed matter systems, whether finite or periodic, metallic or insulating, and with weak to strong electronic correlations. Modern applications of QMC have expanded to cover many of the same systems studied by density functional theory (DFT) and quantum chemical approaches and, in many cases, at a similar atom and electron count, at a far greater computational cost. It shares the same workflow tool, Nexus, which helps simplify and ease application of all the QMC methods by new users and aids in improving reproducibility of complex multi-step research investigations To our knowledge, this is currently the only AFQMC code designed for large scale research calculations that is open source.
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