Local embedding and effective downfolding in the auxiliary-field quantum Monte Carlo method

Abstract

A local embedding and effective downfolding scheme has been developed and implemented in the auxiliary-field quantum Monte Carlo (AFQMC) method. A local cluster in which electrons are fully correlated is defined and the frozen orbital method is used on the remainder of the system to construct an effective Hamiltonian which operates within the local cluster. Local embedding, which involves only the occupied sector, has previously been employed in the context of Co/graphene. Here, the methodology is extended in order to allow for effective downfolding of the virtual sector thus allowing for significant reduction in the computational effort required for AFQMC calculations. The system size which can be feasibly treated with AFQMC is therefore greatly extended as only a single local cluster is explicitly correlated at the AFQMC level of theory. The approximation is controlled by the separate choice of the spatial size of the active occupied region, $R_o$, and of the active virtual region, $R_v$. The systematic dependence of the AFQMC energy on $R_o$ and $R_v$ is investigated and it is found that relative AFQMC energies of physical and chemical interest converge rapidly to the full AFQMC treatment (i.e. using no embedding or downfolding).

References in corpus (13)

• Confined linear carbon chains: A route to bulk carbyne
• A Constrained Path Monte Carlo Method for Fermion Ground States
• Quantum Monte Carlo method using phase-free random walks with Slater determinants
• Density matrix embedding: A strong-coupling quantum embedding theory
• Ab initio computations of molecular systems by the auxiliary-field quantum Monte Carlo method
• Auxiliary-field quantum Monte Carlo calculations of molecular systems with a Gaussian basis
• Phaseless auxiliary-field quantum Monte Carlo calculations with planewaves and pseudopotentials--applications to atoms and molecules
• Quantum Monte Carlo method for the ground state of many-boson systems
• Bond breaking with auxiliary-field quantum Monte Carlo
• Polyyne Electronic and Vibrational Properties under Environmental Interactions
• The Stability, Energetics, and Magnetic States of Cobalt Adatoms on Graphene
• Frozen-orbital and downfolding calculations with auxiliary-field quantum Monte Carlo
• Auxiliary-field quantum Monte Carlo calculations of the molybdenum dimer

Cited by in corpus (8)

• Quantum embedding methods for correlated excited states of point defects: Case studies and challenges
• Local embedding of Coupled Cluster theory into the Random Phase Approximation using plane-waves
• Surface science using coupled cluster theory via local Wannier functions and in-RPA-embedding: the case of water on graphitic carbon nitride
• The Wannier Function Software Ecosystem for Materials Simulations
• Quantum Computation of Reactions on Surfaces Using Local Embedding
• Improved modularity and new features in ipie: Toward even larger AFQMC calculations on CPUs and GPUs at zero and finite temperatures
• Ab initio Calculations in Atoms, Molecules, and Solids, Treating Spin-Orbit Coupling and Electron Interaction on Equal Footing
• Non-perturbative Many-Body Treatment of Molecular Magnets