AI 中文总结
该研究开发了基于STP-DAS框架的4C-MRPT2方法，兼容多种相对论哈密顿量，通过基准计算验证其能高效恢复关联能，揭示布雷特贡献的变化规律，且冻结轨道近似可降低计算成本。
AI 中文摘要
我们提出了一种基于小张量积分布式活性空间（STP-DAS）框架的四分量多参考二阶微扰理论（4C-MRPT2）。该理论公式与狄拉克-库仑（DC）、狄拉克-库仑-冈特（DCG）和狄拉克-库仑-布雷特（DCB）哈密顿量兼容，并继承了内存高效且可大规模并行化的STP-DAS算法，能够对极大的外部空间进行微扰处理。对稀有气体和第13族原子的基准计算表明，4C-MRPT2可高效恢复全电子动态关联，同时为相对论关联效应提供新的见解。计算显示，布雷特对关联能的贡献随原子序数快速增加，对于氙（Xe）约占总关联能的4%。该方法还表明，二阶关联能仅弱依赖于多参考组态参考轨道的选择，且冻结芯和冻结虚轨道近似可大幅降低计算成本，同时精度损失极小。
英文摘要
We present a four-component multireference second-order perturbation theory (4C-MRPT2) within the small tensor product distributed active space (STP-DAS) framework. The formulation is compatible with the Dirac-Coulomb (DC), Dirac-Coulomb-Gaunt (DCG), and Dirac-Coulomb-Breit (DCB) Hamiltonians, and inherits the memory-efficient and massively parallel STP-DAS algorithm, enabling perturbative treatments over very large external spaces. Benchmark calculations on noble-gas and group-13 atoms demonstrate that 4C-MRPT2 efficiently recovers all-electron dynamic correlation while providing new insight into relativistic correlation effects. The calculations show that the Breit contribution to the correlation energy increases rapidly with atomic number and reaches approximately 4% of the total correlation energy for Xe. The method also shows that second-order correlation energies are only weakly dependent on the choice of multiconfigurational reference orbitals, and that frozen-core and frozen-virtual approximations substantially reduce computational cost with minimal loss of accuracy.
Comments18 pages, 4 figures, journal article
