Ergo: An open-source program for linear-scaling electronic structure calculations

Ergo is a C++ program for all-electron Hartree–Fock and Kohn–Sham density functional theory electronic structure calculations using Gaussian basis sets. The program uses algorithms for which the computational cost increases linearly with system size for all parts of the calculation, including computation of the Fock/Kohn–Sham matrix and density matrix construction. Both spin-restricted and unrestricted calculations are supported, and both pure and hybrid density functionals. The program also supports linear-scaling computation of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) vectors. This paper briefly describes how the code is organized and provides examples of how it can be used.