Calculation of the Si–H stretching–bending overtones in SiHCl3 employing ab initio potential energy and dipole moment surfaces

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The Si–H stretching–bending overtones in SiHCl3 were investigated employing theoretically calculated potential energy surfaces (PES) and dipole moment surfaces (DMS). The coupled cluster method CCSD(T) was utilized to generate both one-dimensional (1D) and three-dimensional (3D) surfaces. An empirical 3D PES was also taken into consideration. The computed energy levels and band intensities agree reasonably well with observation for most of the bands. Comparison of CCSD(T) and density functional results for the very weak 2ν1 band shows that it is essential to calculate the DMS at a high level of quantum-chemical theory when cancellation of linear and quadratic contributions to the DMS is significant. The 3D ab initio PES yields more accurate band intensities than the empirical PES and therefore appears to be more realistic.