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What it is

Parsec is a computer code that solves the Kohn-Sham equations by expressing electron wave-functions directly in real space, without use of explicit basis set. The name stands for "Pseudopotential Algorithm for Real-Space Electronic Calculations". It handles periodic boundary conditions (on all three directions) and confined-system boundary conditions. In the latter, the charge density and wave-functions are required to vanish outside a spherical shell enclosing the electronic system. A finite-difference approach is used for the calculation of spatial derivatives. Norm-conserving pseudopotentials are used to describe the interaction between valence electrons and ionic cores (core electrons+nuclei). Owing to the sparsity of the Hamiltonian matrix, the Kohn-Sham equations are solved by direct diagonalization, with the use of extremely efficient sparse-matrix eigensolvers. Besides standard DFT calculations, parsec is able to perform structural relaxation, simulated annealing, Langevin molecular dynamics, polarizability calculations (confined-system boundary conditions only). It can also be used to provide input for TDLDA (time-dependent density functional theory, in adiabatic local-density approximation), GW approximation, and solution of the Bethe-Salpeter equation for optical excitations.

The development of parsec started in the early 1990's with the work of J.R. Chelikowsky, N. Troullier, and Y. Saad ( Phys. Rev. Lett 72, 1240 ; Phys. Rev. B 50, 11355). Later, many people have contributed with additional features and performance improvement:

next up previous contents index
Next: Getting the code Up: Parsec 1.1 User's Guide Previous: Contents   Contents   Index
Murilo Tiago 2005-10-06