Dear Lorenzo, Thank you for your reply. I figured out my problem. You are right, it is not coming from lapack routine.
Regards, Manoj On Fri, 4 Sep 2009, Lorenzo Paulatto wrote: > In data 04 settembre 2009 alle ore 15:54:38, Manoj Srivastava > <manoj at phys.ufl.edu> ha scritto: > > The input is CMACH, I can specify various input variables for 'CMACH' to > > get output, but what variable is returned as output, as there is only one > > in this subroutine? Would you mind having a look at this- its in > > espresso4.0.4/flib/dlamch.f > > > Dear Manoj, > QE does not use simple LAPACK routines for most of its algebra. > Hamiltonian diagonalization is computed using a custom implementation of > the iterative Davidson (or conjugate-gradient) algorithm that only uses > LAPACK to diagonalize a reduced hamiltonian during each iteration. > > Said that, you can control the accuracy to which eigenvalues are computed > cannot be controlled directly by the user (without modifying the code) and > is decreased automatically as the self-consistency approaches convergence. > > The formula used is the following: > ethr = MIN( ethr, 0.1D0*dr2 / MAX( 1.D0, nelec ) ) > where dr2 is the estimated scf accuracy. > As you can see you can increase the accuracy (at convergence) of > eigenvalues and eigenvectors by increasing the convergence threshold. > > > In a more general frame, I think you could disclose some more information > on your "symmetry problem"; personally I doubt it is caused by > insufficient diagonalization accuracy. > > best regards > > -- > Lorenzo Paulatto > SISSA & DEMOCRITOS (Trieste) > phone: +39 040 3787 511 > skype: paulatz > www: http://people.sissa.it/~paulatto/ > > *** save italian brains *** > http://saveitalianbrains.wordpress.com/ > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >