Analytic nuclear forces and molecular properties from full configuration interaction quantum Monte Carlo

Abstract

Unbiased stochastic sampling of the one- and two-body reduced density matrices is achieved in full configuration interaction quantum Monte Carlo with the introduction of a second, "replica" ensemble of walkers, whose population evolves in imaginary time independently from the first, and which entails only modest additional computational overheads. The matrices obtained from this approach are shown to be representative of full configuration-interaction quality, and hence provide a realistic opportunity to achieve high-quality results for a range of properties whose operators do not necessarily commute with the hamiltonian. A density-matrix formulated quasi-variational energy estimator having been already proposed and investigated, the present work extends the scope of the theory to take in studies of analytic nuclear forces, molecular dipole moments and polarisabilities, with extensive comparison to exact results where possible. These new results confirm the suitability of the sampling technique and, where sufficiently large basis sets are available, achieve close agreement with experimental values, expanding the scope of the method to new areas of investigation.

11 pages

References in corpus (4)

• Unbiased Reduced Density Matrices and Electronic Properties from Full Configuration Interaction Quantum Monte Carlo
• The sign problem in full configuration interaction quantum Monte Carlo: Linear and sub-linear representation regimes for the exact wave function
• The effect of quantization on the FCIQMC sign problem
• Hellman-Feynman operator sampling in Diffusion Monte Carlo calculations

Cited by in corpus (19)

• A deterministic alternative to the full configuration interaction quantum Monte Carlo method
• An excited-state approach within full configuration interaction quantum Monte Carlo
• NECI: N-Electron Configuration Interaction with emphasis on state-of-the-art stochastic methods
• The Shape of Full Configuration Interaction to Come
• Density matrices in full configuration interaction quantum Monte Carlo: Excited states, transition dipole moments and parallel distribution
• Developments in Stochastic Coupled Cluster Theory: The initiator approximation and application to the Uniform Electron Gas
• The Adaptive Shift Method in Full Configuration Interaction Quantum Monte Carlo: Development and Applications
• Stochastic Coupled Cluster Theory: Efficient Sampling of the Coupled Cluster Expansion
• Multi-state effective Hamiltonian and size-consistency corrections in stochastic configuration interactions
• Ground- and Excited-State Dipole Moments and Oscillator Strengths of Full Configuration Interaction Quality
• Ground and Excited State First-Order Properties in Many-Body Expanded Full Configuration Interaction Theory
• Fully quantum embedding with density functional theory for full configuration interaction quantum Monte Carlo
• Understanding and Improving the Efficiency of Full Configuration Interaction Quantum Monte Carlo
• Interpolating many-body wave functions for accelerated molecular dynamics on the near-exact electronic surface
• Equation of state of atomic solid hydrogen by stochastic many-body wave function methods
• Full configuration interaction quantum Monte Carlo for coupled electron--boson systems and infinite spaces
• Full Configuration Interaction Excited-State Energies in Large Active Spaces from Subspace Iteration with Repeated Random Sparsification
• Coupled-cluster pairing models for radicals with strong correlations
• Molecular properties from the explicitly connected expressions of the response functions within the coupled-cluster theory