# free chemist

of the hour:

Daniel Hießl

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**OS:** Linux, ....

**License:** Freeware

**Methods:** HF, DFT

###### Single particle two-dimensional numerical functions (orbitals) are used to construct an
antisymmetric many-electron wave function of the restricted open-shell Hartree-Fock
model. The orbitals are obtained by solving the Hartree-Fock equations in the form of the
coupled two-dimensional second-order (elliptic) partial differential equations (PDE). The
Coulomb and exchange potentials are obtained as solutions of the corresponding Poisson
equations. The PDEs are disretized by the 8th-order central difference stencil on a
two-dimensional grid and the resulting large and sparse system of linear equations is
solved by the (multicolour) successive overrelaxation method ((MC)SOR). The
self-consistent-field iterations are interwoven with the (MC)SOR ones and orbital energies
and normalization factors are used to monitor the convergence. The accuracy of solutions
depends mainly on the grid and the system under consideration.

http://www.leiflaaksonen.eu/num2d.html

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