Cioslowski Jerzy, Buchowiecki Marcin
Institute of Physics, University of Szczecin, Wielkopolska 15, 70-451 Szczecin, Poland.
J Chem Phys. 2005 Dec 15;123(23):234102. doi: 10.1063/1.2137322.
Simple approximations to the natural orbitals (NOs) of harmonium with enforced correct short- and long-range asymptotics yield accurate bounds for the NO occupancies. In particular, expressions involving Pade approximants with just one variational parameter are capable of producing the largest NO occupancies with accuracy better than 10(-4). The comparison of two cases with different coupling strengths omega (1.948 51<n<1.948 60 for omega=12 and 1.821 24<n<1.821 29 for omega=110) indicates that the bounds actually become tighter with the increasing extent of correlation. The expressions derived for the most strongly occupied NOs can be readily generalized to all natural orbitals of harmonium.
对具有强制正确短程和长程渐近性的钬自然轨道（NOs）进行简单近似，可得到NO占据数的精确界限。特别是，仅含一个变分参数的帕德近似式所涉及的表达式能够以优于10^(-4)的精度产生最大的NO占据数。对两种不同耦合强度ω的情况进行比较（ω = 12时，1.948 51 < n < 1.948 60；ω = 110时，1.821 24 < n < 1.821 29）表明，随着关联程度的增加，界限实际上变得更紧密。为占据数最多的NOs推导的表达式可以很容易地推广到钬的所有自然轨道。
