Zaccari Daniel, Melo Juan I, Ruiz de Azúa Martín C, Giribet Claudia G
Departamento de Fisica, Facultad de Ciencias Exactas, Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto, Ruta 36, km 601, 5800 Rio Cuarto, Cordoba, Argentina.
J Chem Phys. 2009 Feb 28;130(8):084102. doi: 10.1063/1.3063639.
An alternative approach for the calculation of the electron-positron (e-p) contribution to magnetic properties based on two-component Breit-Pauli spinors is presented. In it, the elimination of the small component scheme is applied to the inverse propagator matrix of e-p pairs. The effect of the positronic manifold is expressed as an operator acting on Breit-Pauli spinors. The operator form thus obtained sums up the relativistic correction as a geometric series and as a result a totally different behavior in the vicinity of a nucleus is obtained as compared to the one of the linear response approximation. This feature has deep influence in numerical values of the e-p contribution to the nuclear magnetic shielding of heavy atoms. Numerical calculations carried out for Kr, Xe, and I show that with this approach, the e-p contributions to this property are in good agreement with those of four-component methods.
提出了一种基于双分量布赖特-泡利旋量计算电子-正电子（e-p）对磁性贡献的替代方法。在该方法中，小分量消除方案应用于e-p对的逆传播子矩阵。正电子流形的效应表示为作用于布赖特-泡利旋量的算符。由此得到的算符形式将相对论修正表示为几何级数，结果与线性响应近似相比，在原子核附近得到了完全不同的行为。这一特性对重原子核磁屏蔽的e-p贡献的数值有深远影响。对氪、氙和碘进行的数值计算表明，采用这种方法，该性质的e-p贡献与四分量方法的结果吻合良好。
