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FreeON
Stable release	1.0.8 / November 8, 2013; 11 years ago
Written in	Fortran, C
Operating system	Linux, FreeBSD, Unix and like operating systems
Type	Computational Chemistry
License	GNU GPLv3
Website	www.nongnu.org/freeon/Vision.html; github.com/FreeON/freeon;

In computer software, FreeON is an experimental, open source (GPL) suite of programs for linear scaling quantum chemistry, formerly known as MondoSCF. It is highly modular, and has been written from scratch for N-scaling SCF theory in Fortran95 and C. Platform independent IO is supported with HDF5. FreeON should compile with most modern Linux distributions. FreeON performs Hartree–Fock, pure density functional, and hybrid HF/DFT calculations (e.g. B3LYP) in a Cartesian-Gaussian LCAO 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 ( $\Gamma$ -point), and an internal coordinate geometry optimizer allows full (atom+cell) relaxation using analytic derivatives. Effective core potentials for energies and forces have been implemented, but Effective Core Potential (ECP) lattice forces do not work yet. Advanced features include O(N) static and dynamic response, as well as time reversible Born Oppenheimer Molecular Dynamics (MD).

Developers

Developer	Affiliation
Matt Challacombe	Los Alamos National Laboratory
Eric Schwegler	Lawrence Livermore National Laboratory
Jessica Tymczak	Houston Community College
Anders M. Niklasson	Los Alamos National Laboratory
Anders Odell	KTH Stockholm
Nicolas Bock	Los Alamos National Laboratory
Karoly Nemeth	Argonne National Laboratory
Valery Weber	University of Zurich
C. K. Gan	Institute for High Performance Computing
Graeme Henkelman	University of Texas at Austin
Robert Snavely	University of Santa Cruz

References

^ 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.
^ Schwegler, E.; Challacombe, M. (1999). "Linear scaling computation of the Fock matrix. IV. Multipole accelerated formation of the exchange matrix". The Journal of Chemical Physics. 111 (14): 6223. Bibcode:1999JChPh.111.6223S. doi:10.1063/1.479926.
^ Schwegler, E.; Challacombe, M. (2000). "Linear scaling computation of the Fock matrix. III. Formation of the exchange matrix with permutational symmetry". Theoretical Chemistry Accounts: Theory, Computation, and Modeling. 104 (5): 344. doi:10.1007/s002140000127. S2CID 94597829.
^ Challacombe, M. (2000). "Linear scaling computation of the Fock matrix. V. Hierarchical Cubature for numerical integration of the exchange-correlation matrix". The Journal of Chemical Physics. 113 (22): 10037–10043. Bibcode:2000JChPh.11310037C. doi:10.1063/1.1316012.