Incomputer software,FreeON is an experimental, open source (GPL) suite of programs for linear scalingquantum chemistry, formerly known as MondoSCF. It is highly modular, and has been written from scratch for N-scaling SCF theory inFortran95 andC. Platform independent IO is supported withHDF5. FreeON should compile with most modern Linux distributions. FreeON performsHartree–Fock, puredensity functional, and hybrid HF/DFT calculations (e.g.B3LYP) in a Cartesian-GaussianLCAO basis. All algorithms are O(N) or O(N lg N) for non-metallic systems.[1][2][3][4][5][6][7] Periodic boundary conditions in 1, 2 and 3 dimensions have been implemented through the Lorentz field (-point), and aninternal coordinate geometry optimizer allows full (atom+cell) relaxation using analytic derivatives. Effective core potentials for energies and forces have been implemented, butEffective Core Potential (ECP) lattice forces do not work yet. Advanced features include O(N) static and dynamic response, as well as time reversible Born OppenheimerMolecular Dynamics (MD).
^Challacombe, M.; Schwegler, E.; Almlöf, J. (1996). "Fast assembly of the Coulomb matrix: A quantum chemical tree code".The Journal of Chemical Physics.104 (12): 4685.Bibcode:1996JChPh.104.4685C.doi:10.1063/1.471163.
^Schwegler, E.; Challacombe, M. (1996). "Linear scaling computation of the Hartree–Fock exchange matrix".The Journal of Chemical Physics.105 (7): 2726.Bibcode:1996JChPh.105.2726S.doi:10.1063/1.472135.
^Challacombe, M.; Schwegler, E. (1997). "Linear scaling computation of the Fock matrix".The Journal of Chemical Physics.106 (13): 5526.Bibcode:1997JChPh.106.5526C.doi:10.1063/1.473575.
^Schwegler, E.; Challacombe, M.; Head-Gordon, M. (1997). "Linear scaling computation of the Fock matrix. II. Rigorous bounds on exchange integrals and incremental Fock build".The Journal of Chemical Physics.106 (23): 9708.Bibcode:1997JChPh.106.9708S.doi:10.1063/1.473833.
