# Analytical & numerical derivatives for forces & vibrations

This directory contains most of the functionality for calculating 1st and 2nd derivatives
of the Fock matrix and interatomic potential corrections with respect to atomic coordinates
for use in force and vibrational calculations.

A significant portion of the analytical derivatives were derived and adapted from
Daniel Liotard's contributions to AMPAC version 2.1 (QCPE No. 506).
