氟氯甲烷CC1_4，CFC1_3，CF_2C1_2，CF_3C1及CF_4的量

本文用量子化学从头计算法在ＨＦ／４－３１Ｇ水平上对氟氯甲烷（ＣＦＣｍｎ）分子作了计算，从分子结构参数及前沿分子轨道组合上做了详细分析。说明了随着Ｆ原子取代ＣＣ１４中Ｃ１原子的增多，分子的各化学健均增强，稳定性增加，ＨＯＭＯ能级降低，ＬＵＭＯ能级升高；ＨＯＭＯ对Ｃ－Ｆ和Ｃ－Ｃ１键都无甚键合作用，ＬＵＭＯ对Ｃ－Ｃ１起反键作用，当ＨＯＭＯ上电子被激发到ＬＵＭＯ上时，分子发生解离。造成大气平流层臭氧消耗的分子光解出来的Ｃ１原子，εＬＵＭＯ与εＨＯＭＯ差值越大，光解需要的紫外光波长越短，发生光解时在大气中的高度越高，大气滞留时间越长，解离出的Ｃ１原子消耗的臭氧分子越多。

The Study of Chlorofluoromethanes CCl_4 CFCl_3, CF_2Cl_2,CF_3Cl and CF_4 by Quantum Chemistry Method

Chlorofluoromethanes were calculated by quantum chemistry abinitiomethod. Molecular structure parameters and HOMO's and LUMO's constitution were analysed. As fluorine atom replaces chlorine atom in CCl4 one by one, the bonds in molecule are strengthened while the valueofεHomois decreased and the value of εLuMois increased. HOMO is unbonding to C-F and C-Cl bondsmeanwhile LUMO is intensively antibonding to C-Cl bonds except for antibonding to C-F bonds inCF4.The molecule will be dissociated when electron is excited from HOMO to LUMO. As a result,thechlorine given by photolysis taken place in stratosphere by molecular oboorbing short-wavelength solarUV radiation which causes electronic excitation from HOMO to LUMO causes ozone depletion.Thebigger the difference between εLUMO and εHOMO is, the higher the photolysis takes place in atmosphereand the longer the atmosphere lifetimes of chloronuoromethanes are.