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

A new four-dimensional(4D) potential energy surface(PES) for the Kr-C2H2 complex including the Q(1) and Q(3) normal modes for the nu(1) symmetric stretching vibration and nu(3) antisymmetric stretching vibration of C2H2 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(3s3p2d1f1g). Two averaged vibra. tional potential energy surfaces of C2H2 at both the vibrational ground and (nu(1), nu(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 theta = 65.6 degrees/114.4 degrees 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-C2H2 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.