A Method for Constructing the Reasonable and Most Contracted Localized Orbitals with Less Computational Efforts

Abstract

Abstract: A method is proposed to construct the reasonable and most contracted localized orbitals with less computational efforts. The non-orthogonalized localized orbitals(NOLMOs) do not possess "orthogonalization tails", thus they are more localized and contracted, and more transferable comparing to the corresponding orthogonalized localized orbitals(OLMOs). Therefore, they are more suitable for use in theoretical study of chemical problems. However, if the orthogonalization requirement is simply removed without imposing other constraints when one intends to construct the most contracted NOLMOs by variation, unreasonable results may be obtained: the NOLMOs tend to linear dependence or they are ill-conditioned linear independence. In this paper, it is proposed that constraining the centriods of NOLMOs at those of the corresponding projected natural bond orbitals(PNBO) can be used to replace the orthogonalization requirement for constructing the reasonable NOLMOs contracted as far as possible(the reasonable most contracted localized orbitals). The calculated results for a series of different kinds of molecules show that, by means of the proposed method, the obtained NOLMOs are linearly independent and reasonably distribute in space, and their spreads are very close to the best results presented in literatures, while the computational efforts decrease considerably. The proposed method can be used to construct the reasonable and most contracted NOLMOs in very large systems due to the fact that the computational efforts for constructing PNBOs only linearly increase with the increase of atoms in systems.

Key words: Non-orthogonalized localized orbitals, Natural bond orbitals, Orbital spread, Reasonable and most contracted localized orbitals

CLC Number:

O641

TrendMD:

FENG Hua-Sheng, BIAN Jiang, LI Le-Min . A Method for Constructing the Reasonable and Most Contracted Localized Orbitals with Less Computational Efforts[J]. Chem. J. Chinese Universities, 2004, 25(7): 1291.

References

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