Gidofalvi Gergely, Mazziotti David A
Department of Chemistry, The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
J Chem Phys. 2007 Jan 14;126(2):024105. doi: 10.1063/1.2423008.
Molecular ground-state energies and two-electron reduced density matrices (2-RDMs) have recently been computed without the many-electron wave function by constraining the 2-RDM to satisfy a complete set of three-positivity conditions for N representability [D. A. Mazziotti, Phys. Rev. A 74, 032501 (2006)]. Energies at both equilibrium and nonequilibrium geometries are obtained within 0.3% of the correlation energy. In this paper the authors extend this work to examine the accuracy of molecular properties, including multipole moments and components of the ground-state energy, relative to full configuration interaction (FCI). Comparisons are also made with 2-RDM methods with two-positivity conditions and two-positivity plus the generalized T1T2 conditions as well as several approximate wave function methods. Using the 2-RDM method with three-positivity conditions, the authors obtain dipole, quadrupole, and octupole moments for BeH2, BH, H2O, CO, and NH3 at equilibrium geometries that are within 0.04% of their FCI values. In addition, for the potential energy surface of N2, the 2-RDM method with three-positivity yields not only accurate total ground-state energies but also accurate expectation values of the kinetic energy operator, the electron-nuclei potential, and electron-electron repulsion.
最近，通过约束二电子约化密度矩阵（2-RDM）以满足N可表示性的一组完整的三正性条件，在不使用多电子波函数的情况下计算了分子基态能量和二电子约化密度矩阵[D. A. 马佐蒂，《物理评论A》74, 032501 (2006)]。在平衡几何结构和非平衡几何结构下获得的能量均在相关能的0.3%以内。在本文中，作者扩展了这项工作，以检验相对于完全组态相互作用（FCI）的分子性质的准确性，包括多极矩和基态能量的分量。还与具有二正性条件、二正性加广义T1T2条件的2-RDM方法以及几种近似波函数方法进行了比较。使用具有三正性条件的2-RDM方法，作者获得了平衡几何结构下BeH2、BH、H2O、CO和NH3的偶极矩、四极矩和八极矩，其值在FCI值的0.04%以内。此外，对于N2的势能面，具有三正性的2-RDM方法不仅能给出准确的总基态能量，还能给出动能算符、电子-核势和电子-电子排斥的准确期望值。
