Perturbation series convergence
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract Møller-Plesset perturbation energies, up to as much as 48th order, have been calculated for H2O (RHF and UHF framework) and NH2 (UHF framework) atC 2v geometries (r e , 1.5r e and 2r e ). Atr e , the RHF and UHF series rapidly converge, but at2r e , the RHF series converges erratically with an energy at 43rd order within 10−7 hartree of the exact value whereas the UHF series converges smoothly, but very slowly, and for H2O has an error in excess of 10−5 hartree at 48th order. The significance of these results is discussed.
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