Relativistic effects on electric properties of many-electron systems in spin-averaged Douglas-Kroll and Pauli approximations
Relativistic effects on electric properties of many-electron systems in spin-averaged Douglas-Kroll and Pauli approximations
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DOI：
10.1063/1.472067
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发表时间：
1996-08-01
影响因子：
4.4
通讯作者：
Hess, BA
中科院分区：
文献类型：
--
作者：
Kello, V;Sadlej, AJ;Hess, BA
采用基于质量-速度和达尔文算符的单分量(标量)相对论近似，以及基于Douglas-Kroll变换的自旋平均非对哈密顿量，研究和比较了相对论效应和电子关联效应对铸币金属氢化物偶极矩的影响。两个运算符中的前一个被发现对CUH和AGH执行得相当准确。对于Auh，泡利近似似乎达到了极限，这可以从与自旋平均的Douglas-Kroll无对形式中获得的值的比较中推断出来。在相对论效应的Douglas-Kroll非对近似下的耦合团簇计算确定了铸币金属氢化物的偶极矩等于1.05A.U。对于CUH，1.14 A.U。Agh和Auh分别为0.52和0.52。相应的非相对论结果分别为1.14、1.36、1.22。讨论了Douglas-Kroll无对近似应用中的一些形式问题。结果表明，由于外部扰动，Hellmann-Feynman定理导致了一阶能量变化的一种相当复杂的形式。然而，通常的期望值公式通过与1/c(4)成比例的项是有效的，并且可以在大多数应用中使用。本文讨论了有限基集上的Douglas-Kroll非对近似的不变性。(C)1996年美国物理研究所。
Relativistic effects and electron correlation effects on the dipole moments of the coinage metal hydrides are investigated and compared employing one-component (scalar) relativistic approximations based on the mass-velocity and Darwin operator and, alternatively, the Douglas-Kroll-transformed spin-averaged no-pair Hamiltonian. The former of the two operators is found to perform quite accurately for CuH and AgH. For AuH the limits of the Pauli approximation seem to be reached, as can be inferred from a comparison with the values obtained within the spin-averaged Douglas-Kroll no-pair formalism. The coupled cluster calculations in the Douglas-Kroll no-pair approximation for relativistic effects establish the dipole moment values of the coinage metal hydrides as equal to 1.05 a.u. for CuH, 1.14 a.u. for AgH and 0.52 for AuH. The corresponding non-relativistic results are 1.14 a.u., 1.36 a.u., and 1.22 a.u., respectively. Some formal problems arising in applications of the Douglas-Kroll no-pair approximation are discussed. It is shown that the Hellmann-Feynman theorem leads to a rather complicated form of the first-order energy change due to external perturbation. The usual expectation value formula is, however, valid through terms proportional to 1/c(4) and can be used in most applications. The invariance property with respect to a shift in the external potential is addressed for the Douglas-Kroll no-pair approximation in a finite basis set. (C) 1996 American Institute of Physics.