Implementation of the Bethe−Salpeter equation in the TURBOMOLE program

A software update solving the Bethe−Salpeter equation (BSE) is reported for the ESCF module of the TURBOMOLE program for the theoretical description of electronically excited states of atoms and molecules. A resolution‐of‐the‐identity (RI) approximation is used for all two‐electron electron‐repulsion integrals that are required for solving the equation. Symmetry is utilized for the point group D 2h and its subgroups, and the BSE approach can be applied in either a spin‐restricted or a spin‐unrestricted Kohn−Sham formalism. Triplet as well as singlet excited states of closed‐shell atoms and molecules can be treated in the spin‐restricted formalism. As a side product, the present software update also allows for the application of the RI approximation to the Hartree−Fock exchange contribution that occurs when a hybrid functional is used in time‐dependent density‐functional theory. © 2016 Wiley Periodicals, Inc.