中文摘要：

采用Gassian09程序包中的多种方法对OH，OCI，HOCl分子的基态结构进行优化计算，优选出QCISD／6—311G（2df），B3P86／6—311＋G（2df）方法分别对OH（X2II），OCI（X2Ⅱ）分子进行计算，得到平衡核间距RoH=0．09696nm，Rocl=0．1569nm，谐振频率w（OH）：3745．37cm-1，w（OCI）=892．046cm-1，与实验结果非常符合．用Murrell—Sorbie势能函数对OH和OCI分子的扫描势能点进行拟合，其扫描点都与四参数Murrell—Sorbie函数拟合曲线符合得很好．优选出QCISD（T）／D95（df,pd）方法对HOCl分子进行计算，得到基态为x1A ＇，键长ROH=0．0966nm，键角∠HOCl=102．3°，谐振频率w1（a1）：738．69cm-1，w2（b2）=1260．25cm-1，离解能De=2．24eV．通过比较发现这些结果与实验值符合得很好，并优于文献报道的结果．随后计算出了力常数，在此基础上，推导出HOCl分子的多体展式势能函数．报道了HOCl分子对称伸缩振动势能图中在H＋OCl→HOCl反应通道上有一鞍点，H原子需要越过1．74eV的能垒才能生成HOCl的稳定结构，在Cl＋OH→HOCl通道上不存在明显势垒，容易形成稳定的HOCl分子．

英文摘要：

The possible ground state structures of OH, OCI and HOCl are optimized by using some methods included in Gaussian 09. Among them, the methods QCISD/6-311G（2df） and B3P86/6-311＋G（2df） are the most suitable for the calculation of OH（X2H） and OCI（X2H） the spacings between eguilibrium nuclei ROH = 0.09696 nm and Rocl = 0.1569 nm, and harmonic freguencies w（OH） = 3745.37 cm-1 and w（OCI） = 892.046 cm-1 are calculated respectively. The calculation results are in good agreement with experimental results, Each potential energy curve obtained via scanning the single point energies of OH and OCI is well fit with the four-parameter Murrell-Sorbie function, according to which spectral data and force constants are deduced. The ground state of HOCl molecule is of 2A1＇ state, and the parameters of structure are Roll = 0.0966 nm, ∠HOCl = 102.3°, w1 （a1） = 738.69 cm-1, w2 （b2） = 1260.25 cm-1, D e = 2.24 eV with QCISD（T）/D95（df, pd）. The present calculation results are in excellent agreement with the experimental values, and they are better than those given in the literature. And the force constants are calculated at the same time. The potential energy function of HOCl is derived from the many-body expansion theory. In the symmetric-stretch potential energy diagram, there is a saddle point in reaction channel H＋OCl→HOCl, and a stable HOCl molecule could be formed only when H atom crosses an energy barrier of 1.74 eV. However there is no clear energy barrier in the reaction channel Cl＋OH→HOCl, therefore a stable HOCl molecule can form easily.