PICVib: an accurate, fast, and simple procedure to investigate selected vibrational modes at high theoretical levels

A new approach Procedure for Investigating Categories of Vibrations (PICVib) for estimating vibrational frequencies of selected modes using only the structure and energy calculations at a more demanding computational level is presented and explored. The PICVib has an excellent performance at only a small fraction of the computational demand required for a complete analytical calculation. The errors are smaller than ca. 0.5% when DFT functionals are combined with high level ab initio methods. The approach is general because it can use any quantum chemical program and electronic structure method. It is very robust because it was validated for a wide range of frequency values (ca. 20-4800 cm(-1)) and systems: XH(3) (D(3h) ) with X = B, Al, Ga, N, P, As, O, S, and Se, YH(4) (D(4h) ) with Y = C, Si, and Ge, conformers of RDX, S(N) 2 and E2 reactions, [W(dppe)(2)(NNC(5)H(10))] complex, carbon nanotubes, and hydrogen-bonded complexes including guanine-cytosine pair.