[Pw_forum] about the number of bands

[Paolo Giannozzi]

On Jun 17, 2007, at 18:55 , Alcantara Ortigoza, Marisol wrote:

> is there any reason why increasing the number of eigenvalues  
> (bands) to be computed improves or speeds the convergence of these,  
> curing the warnings saying that such and such eigenvectors did not  
> convege (usually the highest ones, I read in the forum)?

Davidson diagonalization performs a (conventional) diagonalization in a
subspace containing the trial wavefunctions (the current estimate) and
the estimated corrections ((only for unconverged eigenvectors). If the
subspace is larger, you have more freedom to find the correct ground
state manifold.

Paolo
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Paolo Giannozzi, Democritos and University of Udine, Italy