MTASpec software for calculating the vibrational IR and Raman spectra of large molecules at ab initio level

Fragmentation-based (FB) methods have been developed for enabling ab initio calculations on large molecules and clusters. However, a well-benchmarked FB-based utility, for calculating the vibrational spectra is not available. The present article reports a software package MTASpec, based on the FB-molecular tailoring approach (MTA), for computing the single point energy followed by vibrational IR and Raman spectra for spatially extended molecular systems. Accuracy and efficiency of MTASpec are assessed vis-à-vis their full calculation counterparts for some medium- to large-sized molecular systems using HF, DFT and MP2 theory employing large basis sets. The code is fully automated for use on linux platform, with the Gaussian suite of software at the back-end. It is envisaged that the MTASpec package would enable spectral studies of molecular systems containing ∼100 atoms and/or ∼10000 basis functions employing correlated theories with computational economy.