A decade ago [B. Poirier and A. Salam, J. Chem. Phys. 121, 1704 (2004)], the author introduced the first exact quantum dynamics method proven to defeat the exponential scaling of CPU effort with system dimensionality. It was also shown to achieve perfect efficiency in the limit of large basis size N, meaning that K/N->1 as N->infinity, where K is the number of accurately computed eigenstates. This method, which was applied to model systems with up to 15 degrees of freedom (dofs), uses an orthogonal wavelet basis set, combined with a phase space truncation scheme first proposed by M. Davis and E. Heller. Here, we use a related, but much simpler, momentum-symmetrized phase space Gaussian basis that achieves the same goal. A 'universal' and remarkably simple code has been written, which is dimensionally independent, and which also exploits massively parallel algorithms. The codes have been used to calculate tens of thousands of exact vibrational eigenstates for real molecules such as methyleneimine, acetonitrile, and most recently, benzene.

Toward thirty thousand quantum states of benzene

248th National Meeting (2014)

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