Comparative study of errors in HeH− interaction energy calculations

• Published in: International journal of quantum chemistry Vol. 68; no. 5; pp. 329 - 350
• Main Authors: Shalabi, A. S., Eid, Kh. M., Kamel, M. A., El-Barbary, A. A.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 1998
• Subjects: comparative study of errors; electron correlation; HeH; SCF
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/(SICI)1097-461X(1998)68:5<329::AID-QUA4>3.0.CO;2-X

Basis set truncation error (BSTE), size extensivity Error (SEE), zero point vibrational energy (ZPVE), and basis set superposition error (BSSE) of HeH− weak van der Waals interaction energy were determined and compared at the self‐consistent field (SCF), many‐body perturbation theory (MBPT), and coupled cluster (CC) methods using even‐tempered functions. Isotope substitution effects and the role of bond function augmentation were taken into account. Apart from core correlation energy error (CCEE), which is absent from HeH− interaction energy, the results confirm that BSTE is the most important source of error, followed by SEE of the truncated configuration interaction (CI) expansion, ZPVE and BSSE in a descending order. Introducing quadrable excitations to the truncated CI expansion reduces the magnitude of SEE by ∼45.7%, and BSSE correction is not necessary even at the electron correlation level. While bond function augmentation reduces BSSE at the Hartree–Fock, it has an oscillating behavior at the electron correlation level. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 329–350, 1998