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A comparison of Hartree—Fock, MP2, and DFT results for the HCN dimer and crystal
Author(s) -
Alfredsson Maria,
Ojamäe Lars,
Hermansson K. G.
Publication year - 1996
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1996)60:3<767::aid-qua5>3.0.co;2-v
Subject(s) - hartree–fock method , electronic correlation , dipole , chemistry , lattice energy , coupled cluster , dimer , lattice (music) , atomic physics , molecular physics , physics , crystal structure , molecule , computational chemistry , crystallography , organic chemistry , acoustics
A number of hydrogen‐bond related quantities—geometries, interaction energies, dipole moments, dipole moment derivatives, and harmonic vibrational frequencies—were calculated at the Hartree—Fock, MP2, and different DFT levels for the HCN dimer and the periodic HCN crystal. The crystal calculations were performed with the Hartree—Fock program CRYSTAL92 , which routinely allows an a posteriori electron‐correlation correction of the Hartree—Fock obtained lattice energy using different correlation‐only functionals. Here, we have gone beyond this procedure by also calculating the electron‐correlation energy correction during the structure optimization, i.e., after each CRYSTAL92 Hartree—Fock energy evaluation, the a posteriori density functional scheme was applied. In a similar manner, we optimized the crystal structure at the MP2 level, i.e., for each Hartree—Fock CRYSTAL92 energy evaluation, an MP2 correction was performed by summing the MP2 pair contributions from all HCN molecules within a specified cutoff distance. The crystal cell parameters are best reproduced at the Hartree—Fock and the nongradient‐corrected HF + LDA and HF + VWN levels. The BSSE‐corrected MP2 method and the HF + P91, HF + LDA, and HF + VWN methods give lattice energies in close agreement with the ZPE‐corrected experimental lattice energy. The (HCN) 2 dimer properties are best reproduced at the MP2 level, at the gradient‐corrected DFT levels, and with the B3LYP and BHHLYP methods. © 1996 John Wiley & Sons, Inc.