范德华复合物Kr-C2H2的势能面和振转光谱的理论研究

Theoretical Studies of the Potential Energy Surface and Rovibrational Spectra for Kr-C2H2

采用[CCSD(T)]-F12方法和aug-cc-pVTZ基组,同时引入中心键函数(3s3p2d1f1g)构建了Kr-C2H2体系的高精度四维势能面.在构建势能面时考虑了分子间的振动方式及C2H2单体内的ν1对称伸缩和ν3反对称伸缩振动.将计算得到的四维势能面在Q1方向和Q3方向分别做积分得到C2H2单体分别处于振动基态和(ν1,ν3)=(1,1)激发态的平均势能面.计算结果表明,这2个平均势能面均存在2个等价的T型全局极小值和2个等价线性极小值.全局极小值的几何构型位于R=0.41nm,θ=65.6°/114.4°,势阱深度为151.88cm-1.对径向部分采用离散变量表象法(DVR),角度部分采用有限基组表象法(FBR),并结合Lanczos循环算法计算了Kr-C2H2的振转能级和束缚态.计算结果表明,复合物在(ν1,ν3)=(1,1)区域的带心位移为-1.48cm^-1,表现为红移,与实验值-1.38cm^-1很接近;计算得到的红外跃迁频率也与实验值相吻合,说明得到的从头算势能面具有高精度.

A new four-dimensional(4D) potential energy surface(PES) for the Kr-C 2H 2 complex including the Q 1 and Q 3 normal modes for the ν 1 symmetric stretching vibration and ν 3 antisymmetric stretching vibration of C 2H 2 was studied. The PES was calculated at the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)]-F12 level with augmented correlation-consistent polarized-valence quadruplet-zeta(aug-cc-pVTZ) basis set plus the midpoint bond function(3 s 3 p 2 d 1 f 1 g ). Two averaged vibrational potential energy surfaces of C 2H 2 at both the vibrational ground and (ν 1,ν 3 )=(1,1) excited states were generated from the integration of the four-dimensional potential over the Q 1 and Q 3 coordinates. The averaged potential energy surfaces have two equivalent T-shaped global minima, two equivalent local linear minima as well as three saddle points between the minima. The global minima are located at R = 0.41 nm and θ = 65.6°/114.4° with a well depth of 151.88 cm -1 . The radial discrete variable representation(DVR)/angular finite basis representation(FBR) method and Lanczos algorithm were employed to calculate the rovibrational energy levels and bound states. The calculated vibrational band origin for the Kr-C 2H 2 complex is red shifted by -1.48 cm^ -1 , which is closed to the observed value of -1.38 cm ^-1 . The infrared spectra agree well with the experiment data. The good agreement with the experiment values verifies the high quality of ab initio PESs.