Q-Chem is a general-purpose electronic structure package featuring a variety of established and new methods implemented using innovative algorithms that enable fast calculations of large systems on various computer architectures, from laptops and regular lab workstations to midsize clusters, HPCC, and cloud computing using density functional and wave-function based approaches. It offers an integrated graphical interface and input generator; a large selection of functionals and correlation methods, including methods for electronically excited states and open-shell systems; solvation models; and wave-function analysis tools. In addition to serving the computational chemistry community, Q-Chem also provides a versatile code development platform.

Peter Malcolm Wallace Gill is a New Zealand theoretical and computational chemist known for his contribution to density functional theory (DFT). He is an early and main contributor to the computational chemistry software Q-Chem and was the president of the company during 1998–2013. He is especially known for developing the PRISM algorithm for evaluating two-electron integrals and linear-scaling DFT, as well as self-consistent field method for excited state electronic structure.