BeC，BeC2分子的结构与势能函数

应用密度泛函B3P86/aug-cc-pvtz方法对BeC(X )进行了理论计算，得到BeC分子基态的平衡核间距为0.1666 nm，离解能为2.3185eV，与其它理论结果符合得非常好，并进一步计算了谐振频率为917.9114 cm-1，得到该分子的Murrell-Sorbie势能函数。用QCISD/6-311++G（3df，3pd）方法优化出BeC2(X1A1)分子的稳定构型为C2V，其平衡核间距 =0.1615 nm、 ，并计算了离解能、力常数及谐振频率。在推导BeC2的离解极限基础上，应用多体展式理论方法，推导出基态BeC2分子的解析势能函数，该势能面准确呈现出BeC2`(X1A1)分子基态的结构特征和能量变化。

Study of Rydberg states of sodium in a microwave field using B-spline functions

Equilibrium geometry, force property and spectroscopy property of BeC(X ) molecule have been calculated using the B3P86 method with the basis set aug-cc-pvtz, the equilibrium nuclear distance, dissociation energy and Harmonic frequency are 0.1666 nm, 2.3185 eV and 917.9114 cm-1 respectively, these are in good agreement with the other theorital values, and the Murrell-Sobie potential function of BeC(X ) molecule is obtained. Using the QCISD method with the basis set 6-311++G(3df,3pd), the present work has optimized the equilibrium geometry for the ground state X1A1 of BeC2 ,which is C2v C-Be-C, whose angle, equilibrium nuclear distance and dissociation energy are 46.3203 , 0.1615 nm and 10.37803 eV respectively, and its harmonic frequencies, force constants have been calculated. The present paper correctly determines the dissociation limits, based on group theory and atomic and molecular reactive statics (AMRS). Analytical potential energy function for the ground state X1A1 of BeC2 has been derived using many-body expansion method. The structure and energy of BeC2 can correctly reappear on the potential surface.