Advances in methods and algorithms in a modern quantum chemistry program packageStatement on commercial interests: This paper concentrates on the scientific and technical aspects of Q-Chem 3.0. For the record we (the authors) state that Q-Chem 3.0 is distributed by Q-Chem Inc., which at the time of writing has part-owners including the corresponding author of this paper, M. Head-Gordon, and co-authors P. M. W. Gill, J. Kong, A. I. Krylov, and H. F. Schaefer, III.

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.