CHINESE JOURNAL OF COMPUTATIONAL PHYSICS ›› 2016, Vol. 33 ›› Issue (6): 749-756.

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Analytical Potential Energy Function and Spectra of Li2S Molecule

XU Yongqiang1, PENG Weicheng1, CAI Yuqing2   

  1. 1. College of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China;
    2. School of Science, Xihua University, Chengdu 610039, China
  • Received:2015-09-06 Revised:2016-02-16 Online:2016-11-25 Published:2016-11-25

Abstract: Structures of ground states of Li2, LiS and Li2S molecules are investigated using density function theory B3LYP method and 6-311++g(d,p) basis set. It shows that their electronic states are X1Σg+, X2Πg and X1Σg+. Murrell-Sorbie potential functions with 4 parameters for LiS and Li2 molecules are obtained with nonlinear curve fitting method. Spectral parameters and force constants are studied with Murrel-Sobie potential functions. Analytical potential surface of singlet Li2S is obtained with many-body expansion theory. Rotary contour map, stretching contour map and rotary stretching contour map are reconstructed with analytical potential surface. Static characters of ground singlet Li2S are repeated exactly through these maps. They are equilibrium geometric structure, lowest energy and reasonable chemical reaction channels, respectively. Stretching vibrational contours of potential energy surface show that reaction Li+S+Li→Li2S is a no barrier reaction channel. Reaction channel of S atom attacking Li2 molecule has a transition state. Channel of Li atom attacking LiS molecule has a transition state.

Key words: Li2S, structure, many-body expansion theory, potential energy surface

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