``Q-chem 2.0: A high-performance ab initio electronic structure program package,'' J. Kong, C. A. White, A. I. Krylov, C. D. Sherrill, R. D. Adamson, T. R. Furlani, M. S. Lee, A. M. Lee, S. R. Gwaltney, T. R. Adams, H. Daschel, W. Zhang, P. P. Korambath, C. Ochsenfeld, A. T. B. Gilbert, G. S. Kedziora, D. R. Maurice, N. Nair, Y. Shao, N. A. Besley, P. E. Maslen, J. P. Dombroski, J. Baker, E. F. C. Byrd, T. Van Voorhis, M. Oumi, S. Hirata, C.-P. Hsu, N. Ishikawa, J. Florian, A. Warshel, B. G. Hohnson, P. M. W. Gill, M. Head-Gordon, and J. A. Pople, J. Comp. Chem. 21, 1532-1548 (2000).

Q-Chem 2.0 is a new release of an electronic structure program package, capable of performing first principles calculations on the ground and excited states of molecules using both density functional theory and wave function-based methods. A review of the technical features contained within Q-Chem 2.0 is presented. This article contains brief descriptive discussions of the key physical features of all new algorithms and theoretical models, together with sample calculations that illustrate their performance.