DFTB+ is a fast and efficient versatile quantum mechanical simulation software
package. Using DFTB+ you can carry out quantum mechanical simulations similar to
density functional theory but in an approximate way, typically gaining around
two orders of magnitude in speed.

DFTB+ can be used either as a standalone application or embeded it into other
academic or commercial simulation packages as a library.

WWW: https://dftbplus.org/