Be_2、Mg_2和Ca_2分子高精度键能的量子蒙特卡罗研究

Quantum Monte Carlo study on high precision binding energies of Be_2,Mg_2,Ca_2 molecules

由于Be_2、Mg_2和Ca_2原子存在弱相互作用,尤其是Be_2分子中存在很强的电子关联效应使得精确计算它们的键能存在困难.通过采用量子蒙特卡罗方法和不同初始波函数对Be_2、Mg_2、Ca_2分子的键能进行高精度计算.使用此方法计算的Be_2、Mg_2、Ca_2分子的键能分别为946.97 cm^(-1)、447.3 cm^(-1)、1102.35 cm^(-1),与实验值相比差值仅为17.27 cm^(-1)、23.3cm^(-1)、0.35 cm^(-1).而在密度泛函的研究计算中使用不同的泛函计算的三个分子的键能与实验值之差可达596.4 cm^(-1)、149.5cm^(-1)、335.3cm^(-1).结果表明不同泛函的使用对密度泛函结果影响很大,且密度泛函得到的值与实验值有很大的差异,而量子蒙特卡罗方法计算充分考虑了电子关联效应,得到的结果更接近实验值.

For weakly interacting dimers Be2, Mg2 and Ca2 , it is still difficult to calculate their binding energies accurately, espe- cially when there is a strong electronic correlation effect for Be2 molecule. A research of binding energy of Be2, Mg2 and Ca2 mol- ecules was conducted by Quantum Monte Carlo （QMC） method and different wave functions. The binding energies of Be2, Mg2 and Ca2 molecules calculated by QMC were 946. 97 cm-1 ,447.3 cm-1 and 1102. 35 cm-l, respectively. And the differences a- mong the calculated and experimental values were 17. 27 cm-1 ,23.3 cm1 ,0. 35 cm-1 ,respectively. The differences among bind- ing energies calculated by Density Functional Theory （DFT） and the experimental values of the three molecules might reach 596. 4 cm-1 , 149. 5 cm-l ,335.3 cm-1 , respectively. The results showed that the DFT results were very different from the experi- mental ones, that QMC method fully considered electron correlation effect and that QMC results were closer to the experimental values.