Efficient computation of molecular integrals and their derivatives is a crucial step of molecular property evaluation in modern quantum chemistry. As an integral tensor decomposition technique, the density-fitting (DF) approach becomes a popular tool to reduce the memory and disk requirements for the electron repulsion integrals (ERIs).
Molint framework (MFW) is an application programming interface (API) framework for the computation of molecular integrals and their first derivatives, over contracted Gaussian functions, for the density-fitted methods. The MFW includes overlap, dipole, kinetic, potential, metric, and 3-index integrals and their first derivatives. Furthermore, the MFW provides a smooth approach to build the Fock matrix and evaluate analytic gradients for the density-fitted methods. The MFW is a C++/Fortran hybrid code, which can take advantage of shared-memory parallel programming techniques. The MFW is free software, which can be obtained through an e-mail (ugrbzky@gmail.com) request from the developer (U.B.).