arXiv subjects

Trine Kay Quady

Publications and source records attributed to Trine Kay Quady.

4 recordsLinked to original sources

arXiv2026

Approximating Hartree-Fock theory via an efficiently local reformulation

We explore a reorganized framework for the Hartree Fock equations that allows varying patterns of locality to be imposed on the molecular orbitals while maintaining a highly efficient self-consistent field optimization algorithm. Rather than limiting orbitals' spread and then variationally minimizing the energy within those limits, our reorganization neatly pairs each local degree of freedom with a specific solution condition that itself has a naturally local interpretation. These pairs can each be turned on or off, and, regardless of the sparsity pattern used to make such choices, the overall method maintains a fast self-consistent field optimization. We use this structure to test reaction-matched schemes for imposing orbital locality and, through Fock builds that exploit this locality, achieve competitive timings even in modestly sized molecules. Our initial tests also suggest that this approach to imposed orbital locality can be arranged so as to do minimal damage to both Hartree Fock and MP2 reaction energy predictions.

physics.chem-ph↗

arXiv2025

Selectively enabling linear combination of atomic orbital coefficients to improve linear method optimizations in variational Monte Carlo

Second order stochastic optimization methods, such as the linear method, couple the updates of different parameters and, in so doing, allow statistical uncertainty in one parameter to affect the update of other parameters. In simple tests, we demonstrate that the presence of unimportant orbital optimization parameters, even when initialized to zero, seriously degrade the statistical quality of the linear method's update for important orbital parameters. To counteract this issue, we develop an expand-and-prune selective linear combination of atomic orbitals algorithm that removes unimportant parameters from the variational set on the fly. In variational Monte Carlo orbital optimizations in propene, butene, and pentadiene, we find that large fractions of the parameters can be safely removed, and that doing so can increase the efficacy of the overall optimization.

physics.chem-ph↗

arXiv2025

Aufbau suppressed coupled cluster as a post-linear-response method

We investigate the ability of Aufbau suppressed coupled cluster theory to act as a post-linear-response correction to widely used linear response methods for electronically excited states. We find that the theory is highly resilient to shortcomings in the underlying linear response method, with final results from less accurate starting points nearly as good as those from the best starting points. This pattern is especially stark in charge transfer states, where the approach converts starting points with multi-eV errors into post-linear-response results with errors on the order of 0.1 eV. These findings highlight the ability of Aufbau suppressed coupled cluster to perform its own orbital relaxations and raise the question of whether initializing it with an orbital relaxed reference is worth the trouble.

physics.chem-ph↗

arXiv2024

Method-independent cusps for atomic orbitals in quantum Monte Carlo

We present an approach for augmenting Gaussian atomic orbitals with correct nuclear cusps. Like the atomic orbital basis set itself, and unlike previous cusp corrections, this approach is independent of the many-body method used to prepare wave functions for quantum Monte Carlo. Once the basis set and molecular geometry are specified, the cusp-corrected atomic orbitals are uniquely specified, regardless of which density functionals, quantum chemistry methods, or subsequent variational Monte Carlo optimizations are employed. We analyze the statistical improvement offered by these cusps in a number of molecules and find them to offer similar advantages as molecular-orbital-based approaches while maintaining independence from the choice of many-body method.

physics.chem-ph↗