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Choice of the k-point mesh

  For a periodic system, integrals in real space over the (infinitely extended) system are replaced by integrals over the (finite) first Brillouin zone in reciprocal space, by virtue of Bloch's theorem. In fhi98md, such integrals are performed by summing the function values of the integrand (for instance: the charge density) at a finite number of points in the Brillouin zone, called the k-point mesh.  Choosing a sufficiently dense mesh of integration points is crucial for the convergence of the results, and is therefore one of the major objectives when performing convergence tests. Here it should be noted that there is no variational principle governing the convergence with respect to the k-point mesh. This means that the total energy does not necessarily show a monotonous behavior when the density of the k-point mesh is increased.

 


next up previous contents index
Next: Total Energy Minimization Schemes Up: Step-by-step description of calculational Previous: How to set up
Matthias Wittenberg
1999-08-06