Application of state-specific multireference Moeller-Plesset perturbation theory to nonsinglet states
- Department of Physics, Taki Government College, Taki, North 24, Parganas-743429 (India)
- Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711 103 (India)
- Indian Institute of Astrophysics, Bangalore 560034 (India)
We present molecular applications of a spin free size-extensive state-specific multireference perturbation theory (SS-MRPT), which is valid for model functions of arbitrary spin and generality. In addition to the singlet states, this method is equally capable to handle nonsinglet states. The formulation based on Rayleigh-Schroedinger approach works with a complete active space and treats each of the model space functions democratically. The method is capable of handling varying degrees of quasidegeneracy and of ensuring size consistency as a consequence of size extensivity. In this paper, we illustrate the effectiveness of the Moeller-Plesset (MP) partitioning based spin free SS-MRPT [termed as SS-MRPT(MP)] in computations of energetics of the nonsinglet states of several chemically interesting and demanding molecular examples such as LiH, NH{sub 2}, and CH{sub 3}. The spectroscopic constants of {sup 3}{sigma}{sup -} state of NH and OH{sup +} molecular systems and the ground {sup 1}{sigma}{sub g}{sup +} as well as excited {sup 3}{sigma}{sub u}{sup +} states of N{sub 2} have been investigated and comparison with experimental and full configuration interaction values (wherever available) has also been provided. We have been able to demonstrate here that the SS-MRPT(MP) method is an intrinsically consistent and promising approach to compute reliable energies of nonsinglet states over different geometries.
- OSTI ID:
- 21254978
- Journal Information:
- Journal of Chemical Physics, Vol. 130, Issue 1; Other Information: DOI: 10.1063/1.3043364; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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