精确计算分子核性质的两步法
Two-step method for precise calculation of core properties in molecules
摘要：
重原子系统的核性质是由原子核中大量集中的算符描述的，如超精细结构和P，T-宇称不守恒效应，精确计算这些性质通常需要考虑相对论效应。不幸的是，完全相对论处理含有重元素的分子是非常消耗已经在计算和转换的阶段的两个电子积分与一组基本的四分量旋量。反过来，相对论有效实势（RECP）计算价（光谱，化学等）。由于RECP方法可以很好地处理分子价电子的相关性和相对论性效应，并大大减少了计算工作量，因此分子性质的计算是非常受欢迎的。原子核中的价分子旋量通常是平滑的，因此直接计算重核附近的电子密度是不可能的。本文讨论了在对分子进行二分量RECP计算后，对原子核中四分量旋量的正确形状进行非变分和变分单中心恢复的方法。它们的效率在重原子分子YbF，BaF，TlF和PbO的超精细结构和宇称不守恒效应的相关计算中得到了说明。
英文摘要：
Precise calculations of core properties in heavy-atom systems which are described by the operators heavily concentrated in atomic cores, like to hyperfine structure and P,T-parity nonconservation effects, usually require accounting for relativistic effects. Unfortunately, completely relativistic treatment of molecules containing heavy elements is very consuming already at the stages of calculation and transformation of two-electron integrals with a basis set of four-component spinors. In turn, the relativistic effective core potential (RECP) calculations of valence (spectroscopic, chemical etc.) properties of molecules are very popular because the RECP method allows one to treat quite satisfactory the correlation and relativistic effects for the valence electrons of a molecule and to reduce significantly the computational efforts. The valence molecular spinors are usually smoothed in atomic cores and, as a result, direct calculation of electronic densities near heavy nuclei is impossible. In the paper, the methods of nonvariational and variational one-center restoration of correct shapes of four-component spinors in atomic cores after a two-component RECP calculation of a molecule are discussed. Their efficiency is illustrated in correlation calculations of hyperfine structure and parity nonconservation effects in heavy-atom molecules YbF, BaF, TlF, and PbO.
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