Large Scale Exact Quantum Dynamics Calculations: Using Phase Space to Truncate the Basis Effectively

Poirier, Bill

doi:10.1002/9781119374978.ch9

Cited by 3 publications

(1 citation statement)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Computational resources can be saved by judiciously truncating a lattice of Gaussian bases or adjusting the Gaussian forms, as demonstrated by Poirier. 29 In line with this direction, Frankcombe et al 30,31 proposed a way of efficiently preparing time-independent Gaussian bases for a given wave function, called the basis expansion leaping multiconfiguration Gaussian (BEL MCG) method. For a time-independent basis set, the wave packet propagation is performed by solving the equations of motion for expansion coefficients only.…”

Section: Introductionmentioning

confidence: 99%

A Structure-Based Gaussian Expansion for Quantum Reaction Dynamics in Molecules: Application to Hydrogen Tunneling in Malonaldehyde

et al. 2023

View full text Add to dashboard Cite

We developed an approximate method for quantum reaction dynamics simulations, namely, a structure-based Gaussian (SBG) expansion approach, where SBG bases for the expansion of the wave function Ψ, expressed by a product of single-atom Cartesian Gaussians centered at the positions of respective nuclei, are mainly placed around critical structures on reaction pathways such as on the intrinsic reaction coordinate (IRC) through a transition state. In the present approach, the "pseudo-lattice points" at which SBGs are deployed are selected in a perturbative manner so as to make moderate the expansion length. We first applied the SBG idea to a two-dimensional quadruple-well model and obtained accurate tunneling splitting values between the lowest four states. We then applied it to hydrogen tunneling in malonaldehyde and achieved a tunneling splitting of 27.1 cm −1 with only 875 SBGs at the MP2/6-31G(d,p) level of theory, in good agreement with 25 cm −1 by the more elaborate multiconfiguration time-dependent Hartree method. Reasonable results were also obtained for singly and doubly deuterated malonaldehyde. We analyzed the tunneling states by utilizing expansion coefficients of individual SBGs and found that 40−45% of the SBGs in Ψ are nonplanar structures and SBGs away from the IRC contribute a little to hydrogen transfer.

show abstract

Section: Introductionmentioning

confidence: 99%

A Structure-Based Gaussian Expansion for Quantum Reaction Dynamics in Molecules: Application to Hydrogen Tunneling in Malonaldehyde

et al. 2023

View full text Add to dashboard Cite

show abstract

Using phase-space Gaussians to compute the vibrational states of OCHCO+

Pandey

Poirier

2019

The Journal of Chemical Physics

View full text Add to dashboard Cite

In this article, we use momentum-symmetrized phase-space Gaussians to calculate the vibrational energy eigenstates of the OCHCO+ cation. A potential energy surface provided by Bowman’s group was used, albeit refit to a sixth order anharmonic force field. We have developed the “Crystal” algorithm to implement various basis set truncation strategies for our calculations. These calculations were performed using the SwitchBLADE code, designed by our group, which constructs and diagonalizes the vibrational Hamiltonian matrix in order to compute energy eigenstates. A theoretical overview of the Crystal algorithm is presented, as is a discussion of how best to truncate the basis for a floppy double-well system. Specific vibrational transition frequency results for OCHCO+ are also presented and analyzed.

show abstract

Exact matrix elements for general two-body central-force interactions, expressed as sums of products

2018

View full text Add to dashboard Cite

Large Scale Exact Quantum Dynamics Calculations: Using Phase Space to Truncate the Basis Effectively

Cited by 3 publications

References 42 publications

A Structure-Based Gaussian Expansion for Quantum Reaction Dynamics in Molecules: Application to Hydrogen Tunneling in Malonaldehyde

A Structure-Based Gaussian Expansion for Quantum Reaction Dynamics in Molecules: Application to Hydrogen Tunneling in Malonaldehyde

Using phase-space Gaussians to compute the vibrational states of OCHCO+

Exact matrix elements for general two-body central-force interactions, expressed as sums of products

Contact Info

Product

Resources

About