A comparison of Hartree—Fock, MP2, and DFT results for the HCN dimer and crystal

✍ Scribed by Maria Alfredsson; Lars Ojamäe; K. G. Hermansson

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 806 KB
• Volume: 60
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1996)60:3<767::aid-qua5>3.0.co;2-v

✦ Synopsis

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 electroncorrelation 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-correcfed 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), dimer properties are best reproduced at the MP2 level, at the gradient-corrected DFT levels, and with the B3LYP and BHHLYP methods. 0 1996 John Wiley & Sons, Inc. the computational and quantum chemists. The challenge arises from the complicated nature of hydrogen-bonded interactions, and the irrefutable importance is due to all the biological and physiological processes where hydrogen bonds play a vital role.