The development of accurate multi-component molecular theory for quantum simulation of hydrogen-bonding and positronic systems

近年来，我们一直在发展一些新的第一性原理方法，以量子力学的方式处理包括电子和原子核（正电子）在内的多组分系统。为了包括新的多体贡献，如电子-核和核-核相关，我们发展了(1)多组分密度泛函理论（MC DFT）和(2)多组分量子蒙特卡罗（MC QMC）方法。MC - DFT的发展：我们定义了多分量DFT （MC - DFT）的Kohn-Sham算子，并推导了关于经典核坐标的总能量和梯度的解析方程。利用MC DFT方法对卟啉和卟啉分子的H/D同位素效应进行了电子相关分析，证实了我们的结果与相应的实验值有较好的一致性。在以氘取代内部氢的hd物质中，这种高度对称的几何结构被打破，引起的电子极化急剧增加，偶极矩值发生了变化。这些结果清楚地表明质子和氘核之间量子性质的差异影响了电子结构和分子几何形状。为了提高MC （HF+DFT）方法的准确性，我们还在collei - salvetti相关泛函的基础上建立了新的电子-核相关泛函。MC - QCM的发展：为了定量准确地分析正电子分子化合物，我们开发了多组分量子蒙特卡罗（MC - QMC）方法，并将其应用于[H: e+]1和[HCN: e^+]体系的正电子化合物。对于[H: e^+]系统，虽然变分蒙特卡罗计算结果较差，但扩散蒙特卡罗计算结果与hylleraas型波函数计算结果吻合较好。我们的结果-0.788949 (82)hartree比使用单中心高斯型基函数的全组态相互作用方法的结果要低得多。以[HCN: e^+]体系为例，据我们所知，斯特拉斯堡在2006年报告的最精确能量为-92.901915哈特里。另一方面，我们通过VMC和DMC方法分别获得了-93.2591(5)和-93.39830 (8)hartree，并创造了世界纪录的变分能量！少

Recently, we have been developing some new first-principles approaches which treat multi component systems including both electrons and nuclei(positron)quantum-mechanically. To include the new many-body contribution such as electron-nuclei and nuclei-nuclei correlations, we have developed(1)multi-component density functional theory (MC DFT) and (2) multi-component quantum Monte Carlo (MC QMC)methods.1.Development of MC DFT: We have defined Kohn-Sham operators for multi-component DFT (MC DFT) ,and derived analytical equations for total energy and gradient with respect to classical nuclear coordinates. Using MC DFT method, we have analyzed the H/D isotope effect of porphine and porphycene molecules with electron correlation, and confirmed that our results are in reasonable agreement with the corresponding experimental values. In the HD-species which replaced an inner-hydrogen to a deuterium, such high-symmetric geometries are broken down and the induced electronic polarization drasticall … More y changes the dipole moment values. These results clearly indicate that the difference of quantum nature between proton and deuteron influences the electronic structure and molecular geometry. Tb improve accuracy of our MC (HF+DFT) method, we have also developed a new electron-nucleus correlation functional based on the Colle-Salvetti correlation functional.2.Development of MC QCM: In order to analyze the positron-molecular compounds with quantitative accuracy, we have developed the multi-component quantum Monte Carlo (MC QMC) method, and applied to the positronic compounds of[H: e+]1 and [HCN: e^+]systems. Although the variational Monte Carlo calculation gives poor results in the case of [H: e^+] system, the diffusion Monte Carlo result is in good agreement with that by Hylleraas-type wave function. Our result of -0.788949 (82) hartree is much lower than that using the full-configuration interaction method with one-centered Gaussian type basis functions. In the case of [HCN: e^+]system, to our knowledge, the most accurate energy is reported as -92.901915 hartree in 2006 by Strasburg. On the other hand, we have obtained -93.2591 (5) and -93.39830 (8) hartree by VMC and DMC method, and achieved the WORLD RECORD variational energy! Less