Pak Michael V, Chakraborty Arindam, Hammes-Schiffer Sharon
Department of Chemistry, 104 Chemistry Building, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Phys Chem A. 2009 Apr 23;113(16):4004-8. doi: 10.1021/jp810410y.
The nuclear-electronic orbital explicitly correlated Hartree-Fock (NEO-XCHF) method is modified and extended to study electron-positron quantum systems. The NEO-XCHF method is more computationally efficient than the explicitly correlated methods previously applied to positron systems because only the electron-positron dynamical correlation is treated explicitly in NEO-XCHF. As a result, the form of the wave function is much simpler with fewer parameters, and the variational optimization of the molecular orbital parameters is performed through an iterative scheme rather than a stochastic optimization. The NEO-XCHF approach is used to calculate the positron annihilation rate for positronium hydride (PsH). The resulting annihilation rate for PsH is within 20% of the most accurate values available and is calculated at a fraction of the computational cost. These results suggest that qualitatively accurate positron annihilation rates can be calculated treating only electron-positron correlation explicitly, leading to significant computational savings by neglecting electron-electron dynamical correlation. Thus, the NEO-XCHF approach could potentially enable the calculation of qualitatively accurate positron annihilation rates for larger positron systems.
对核 - 电子轨道显式相关哈特里 - 福克（NEO - XCHF）方法进行了修改和扩展，以研究电子 - 正电子量子系统。NEO - XCHF方法比先前应用于正电子系统的显式相关方法在计算上更高效，因为在NEO - XCHF中仅显式处理电子 - 正电子动态相关。因此，波函数的形式更简单，参数更少，并且分子轨道参数的变分优化是通过迭代方案而不是随机优化来进行的。NEO - XCHF方法用于计算氢化正电子素（PsH）的正电子湮灭率。得到的PsH湮灭率在现有最精确值的20%以内，并且计算成本仅为其一小部分。这些结果表明，仅显式处理电子 - 正电子相关就可以计算出定性准确的正电子湮灭率，通过忽略电子 - 电子动态相关可大幅节省计算量。因此，NEO - XCHF方法有可能用于计算更大正电子系统的定性准确的正电子湮灭率。
