Evaluating VPT2 schemes for accurate automated thermochemistry and spectroscopy for non-covalent systems

Welch, Bradley

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https://hdl.handle.net/2142/104435 Copy

Description

Title

Evaluating VPT2 schemes for accurate automated thermochemistry and spectroscopy for non-covalent systems

Author(s)

Welch, Bradley

Contributor(s)

• Bross, David H.
• Ruscic, Branko
• Quintas Sánchez, Ernesto
• Dawes, Richard

Issue Date

2019-06-19

Keyword(s)

• Electronic structure
• Potential energy surfaces

Abstract

High level computational thermochemical protocols take an additive approach to computing the total energy of a molecular system. For small systems, components related to the electronic structure can be systematically converged using methods such as coupled-cluster theory at the complete basis limit. The vibrational level pattern (and at 0 K the zero-point energy, ZPE) yields a relatively large contribution and is thus a possible source of significant error. An inaccurate ZPE leads to poor quantities such as enthalpies of formation and hence interpretations in kinetics and dynamics. As a result an accurate determination of this one term is critical and the focus of this talk. Accurate anharmonic models such as VPT2 and VCI exist for semi-rigid molecules in the gas phase. Non-covalent systems are also of importance in a wide range of areas. The VPT2 model has not been applied as widely to non-covalent systems and questions remain as to its general applicability. Here, a screening of low-cost implementations of VPT2 calculations were performed for a series of vdW systems as large as Benzene-Ar. The screening was done with an automated thermochemical protocol. Comparisons are made with full-dimensional variational calculations using global potential energy surfaces, and to experimental data where available.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/104435

DOI

https://doi.org/10.15278/isms.2019.WD05

Copyright and License Information

Copyright 2019 Bradley Welch

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