Geometry Predictions, Vibrational Analysis and IR Intensities of XH₃Y (X=C, Si, Ge, Y=F, Cl, Br) Calculated by Hybrid Density Functional Theory, MP2 and MP4 Methods

Abraham F. Jalbout^a,*, Bartosz Trzaskowski^b,*, Yuanzhi Xia^c, Yahong Li^c,d
a Institute de Quimica, Universidad Nacional Autonomaa de Mexico, Mexico City, Mexico
^b Department of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
^c Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China
^d Department of Chemistry, Suzhou University, Suzhou 215006, China
E-mail: trzask@email.arizona.edu

Abstract
Hybrid density functional theory B3LYP, B1LYP, B3P86, MPW1PW91 and B3PW91 methods as well as MP2 and MP4 methods at the 6-311++G (3df,3pd) level of theory are used for the calculations of geometrical parameters, infrared vibrational frequencies and absorption intensities of XH₃Y (X=C, Si, Ge and Y=F, Cl, Br) set of molecules. All of the calculated results are compared with the most recent experimental data. The advantages of DFT methods are exhibited from the comparison and discussion. The basis set effect is also considered and the optimal theoretical methods for the discussed systems are recommended.

Keywords: Halogenated methane, halogenated silane, halogenated germane, vibrational analysis, density functional theory