Accurate equilibrium inversion barrier of ammonia by extrapolation to the one-electron basis set limit

Abstract

A scheme based on treating uniform singlet-pair and triplet-pair interactions is suggested to extrapolate electron correlation energy of ammonia, calculated at two basis-set levels of ab initio theory in the infinite one-electron basis-set limit. The dual-level method is tested on the extrapolation of the full correlation in coupled-cluster singles and doubles and in the case also a noniterative perturbative correction for connected triple energies for the C 3v and D 3h structures of ammonia, with correlation-consistent basis sets of the type cc-pVXZ (X = D, T, Q, 5, 6) and aug-cc-pVXZ (X = D, T, Q, 5). For testing and comparison purposes, the energies reported by Klopper [J. Comput. Chem. 22 1306 (2001)] have been taken. From a corresponding extrapolation of CCSD(T)/AVXZ energies for X = 4, 5, we obtain total inversion barriers of 1833.87 cm −1 /1832.33 cm −1 for the two/three-parameter extrapolation rules, which are in good agreement with other theoretical extrapolation and empirical values in the literature.

Stereochemistry of Simple Molecules inside Nanotubes and Fullerenes: Unusual Behavior of Usual Systems

“…Recent years exhibit a significant interest to the investigation of pyramidal inversion in XH 3 compounds [233]. One of the main challenges facing the theoretical spectroscopy is connected with a selection of ab initio and DFT methods that can ensure the accurate estimate the energy of nitrogen inversion barrier [234]. Authors of [235] suggested a benchmark set that comprises 24 high-level wave-function inversion barriers in different compounds; it is submitted that at least medium-sized triple-split-valence basis sets with at least one set of polarization functions should be used for the theoretical study of pyramidal inversion.…”

Choosing the optimal basis set for the correct assessment of the barrier pyramidal inversion of trimethylamine by PBE

“…Заметный интерес к исследованию пирамидальной инверсии соединений трехвалентного азота [1] вызывает необходимость корректного выбора подходящих расчетных методов и базисных наборов, позволяющих получить близкое к данным эксперимента значение барьера пирамидальной инверсии конкретного амина [2,3]. Сама по себе эта проблема решается выбором подходящего метода ab initio в сочетании с расширенным либо корреляционно-согласованным базисным набором.…”