We have incorporated MPI based parallelism with dynamic load balance into the Hartree–Fock and DFT modules of Q-Chem. A series of benchmark calculations consisting of both single point energy and gradient calculations were carried out to gauge the performance of the parallel modules. Calculations were carried out on two different parallel computers, namely a shared memory Silicon Graphics Origi...

nowadays nmr spectroscopy becomes a powerful tool in chemistry because of the nmr chemical shifts. hartree–fock theory and the gauge-including atomic orbital (giao) methods are used in the calculation of 29si nmr chemical shifts of various silicate species in the silicate solution as initial components for zeolite synthesis both in gas and solution phase. calculations have been performed at geo...

We present an efficient theory and algorithm for computing four-component relativistic Dirac-Fock wave functions using the Coulomb, Gaunt, and full Breit interactions. Our implementation is based on density fitting, and is routinely applicable to systems with 100 atoms and a few heavy elements. The small components are expanded using 2-spinor basis functions. We show that the factorization of 3...