View source for FreeON

{{distinguish|Freon}}
{{Multiple issues|
{{Notability|Products|date=October 2021}}
{{COI|date=October 2021}}
{{Primary sources|date=October 2021}}
}}
{{Infobox software
|name = FreeON
|logo = FreeON notext logo.jpg
|logo size = 72px
|developer =
|latest_release_version = 1.0.8
|latest_release_date = {{Start date and age|2013|11|08}}
| programming language = [[Fortran]], [[C (programming language)|C]]
|operating_system = [[Linux]], [[FreeBSD]], [[Unix]] and [[Unix-like|like]] operating systems
|genre = [[Computational Chemistry]]
|license = [[GNU General Public License|GNU GPLv3]]
| website = {{ubl|{{URL|http://www.nongnu.org/freeon/Vision.html}}|{{URL|https://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 [[Fortran|Fortran95]] and [[C (programming language)|C]]. Platform independent IO is supported with [[HDF5]]. FreeON should compile with most modern Linux distributions. FreeON performs [[Hartree–Fock]], pure [[density functional theory|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.<ref>{{Cite journal | last1 = Challacombe | first1 = M. | last2 = Schwegler | first2 = E. | last3 = Almlöf | first3 = J. | doi = 10.1063/1.471163 | title = Fast assembly of the Coulomb matrix: A quantum chemical tree code | journal = The Journal of Chemical Physics | volume = 104 | issue = 12 | pages = 4685 | year = 1996 |bibcode = 1996JChPh.104.4685C }}</ref><ref>{{Cite journal | last1 = Schwegler | first1 = E. | last2 = Challacombe | first2 = M. | doi = 10.1063/1.472135 | title = Linear scaling computation of the Hartree–Fock exchange matrix | journal = The Journal of Chemical Physics | volume = 105 | issue = 7 | pages = 2726 | year = 1996 |bibcode = 1996JChPh.105.2726S }}</ref><ref>{{Cite journal | last1 = Challacombe | first1 = M. | last2 = Schwegler | first2 = E. | doi = 10.1063/1.473575 | title = Linear scaling computation of the Fock matrix | journal = The Journal of Chemical Physics | volume = 106 | issue = 13 | pages = 5526 | year = 1997 |bibcode = 1997JChPh.106.5526C }}</ref><ref>{{Cite journal | last1 = Schwegler | first1 = E. | last2 = Challacombe | first2 = M. | last3 = Head-Gordon | first3 = M. | doi = 10.1063/1.473833 | title = Linear scaling computation of the Fock matrix. II. Rigorous bounds on exchange integrals and incremental Fock build | journal = The Journal of Chemical Physics | volume = 106 | issue = 23 | pages = 9708 | year = 1997 |bibcode = 1997JChPh.106.9708S }}</ref><ref>{{Cite journal | last1 = Schwegler | first1 = E. | last2 = Challacombe | first2 = M. | doi = 10.1063/1.479926 | title = Linear scaling computation of the Fock matrix. IV. Multipole accelerated formation of the exchange matrix | journal = The Journal of Chemical Physics | volume = 111 | issue = 14 | pages = 6223 | year = 1999 |bibcode = 1999JChPh.111.6223S | url = https://zenodo.org/record/1232067 }}</ref><ref>{{Cite journal | last1 = Schwegler | first1 = E. | last2 = Challacombe | first2 = M. | doi = 10.1007/s002140000127 | title = Linear scaling computation of the Fock matrix. III. Formation of the exchange matrix with permutational symmetry | journal = Theoretical Chemistry Accounts: Theory, Computation, and Modeling | volume = 104 | issue = 5 | pages = 344 | year = 2000 | s2cid = 94597829 | url = https://zenodo.org/record/1232633 }}</ref><ref>{{Cite journal | last1 = Challacombe | first1 = M. | title = Linear scaling computation of the Fock matrix. V. Hierarchical Cubature for numerical integration of the exchange-correlation matrix | doi = 10.1063/1.1316012 | journal = The Journal of Chemical Physics | volume = 113 | issue = 22 | pages = 10037–10043 | year = 2000 |bibcode = 2000JChPh.11310037C | url = https://zenodo.org/record/1231848 }}</ref> Periodic boundary conditions in 1, 2 and 3 dimensions have been implemented through the Lorentz field (<math>\Gamma</math>-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==

{| class="wikitable sortable" 
|-
! 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
|}

==See also==
*[[List of quantum chemistry and solid state physics software]]

==References==
<references/>

{{Chemistry software}}
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[[Category:Computational chemistry software]]