Theoretical studies on vibrational spectra of ClC(O)NCS

The optimized geometries, vibrational force fields and infrared intensities of tracts and cis forms of CIC(O)NCS were calculated by density functional theory (DFT) method with 6-31G* basis set. The theoretical force fields of B3LYP/6-31G* were scaled by using the scaled quantum mechanical (SQM) forc e field method. The scale factors were taken from the previous results of P ulay. The average deviations between the experimental and computed frequenc ies are 7.3 and 8.1 cm(-1) for the trans- and cis- isomers of CIC(O)NCS, re spectively. The assignments of the fundamentals for the two rotational conf ormers of this molecule were also performed according to the potential ener gy distribution (PED) and the infrared intensities.