Dear vZacharias, is your criterion also correct regarding convergence with resperct to the k-grid?
I'm asking because in this case I reach convergence already with a 1x2x2 mesh and this seems to me a very little amount of grid-points. Thanks and Regards Stephan -----Original message----- From: Ludwig, Stephan <[email protected]> Sent: Wednesday 12th August 2015 20:00 To: [email protected] Subject: RE: [SIESTA-L] When is convergence reached? Thank you Zacharias -----Original message----- From: [email protected] <[email protected]> Sent: Wednesday 12th August 2015 19:45 To: [email protected] Subject: RE: [SIESTA-L] When is convergence reached? Try to find the convergence in terms of energy per atom. What you will find is that your energy is converged with accuracy less than 1meV/atom. This accuracy is good enough for band structure calculations. Therefore, convergence has already been reached for a 200 mesh cutoff. Zacharias Fthenakis > Hi, > > thank you for the reply my unit cell is rather big (at least for a solid). > Its an organic salt with 236 atoms. > > Cell volume = 2905.615438 Ang**3 > > : Cell vector modules (Ang) : 32.783000 11.179003 7.999052 > > > > In the first step I want to study bandstructure DOS and PDOS. > > Later optical excitations. > > > > Can you tell when I can call the system convergent wrt the total energy. > > > > Thanks and Regards > > Stephan > > > > -----Original message----- > From: [email protected] <[email protected]> > Sent: Tuesday 11th August 2015 18:52 > To: [email protected] > Subject: Re: [SIESTA-L] When is convergence reached? > > > Hi Stephan, > it depends on how big is your unit cell and what you want to study. > >> Hi, >> >> I've a question concerning the convergence criterion. >> >> Let's say I want to examine convergence of the total energy a system >> with >> respect to the meshcutoff. >> >> When is convergence reached? Is it reached when there is no change in >> the >> first digit after the comma >> >> like in the following example: >> >> meshcutoff total energy >> >> 150 -42994.1019 >> >> 170 -42994.116 >> >> 190 -42994.127 >> >> 210 -42994.133 >> >> >> >> or is it usefull to continue the test till there is no change in the >> second digit after the comma? >> >> What is a sensible criterion for convergence? >> >> >> >> Thanks and regards >> >> >> >> Stephan Ludwig >> >> > > > ********************************************************* > Dr Zacharias G. Fthenakis > Research Associate > Institute of Electronic Structure and Laser (I.E.S.L.) > Foundation for Research and Technology Hellas (FO.R.T.H.) > Vassilika Vouton P.O. Box 1527 71003 Heraklion Crete Greece > Phone +30 2810 391824 > FAX +30 2810 391305 > webpage: http://esperia.iesl.forth.gr/˜fthenak > ********************************************************** > > > ********************************************************* Dr Zacharias G. Fthenakis Research Associate Institute of Electronic Structure and Laser (I.E.S.L.) Foundation for Research and Technology Hellas (FO.R.T.H.) Vassilika Vouton P.O. Box 1527 71003 Heraklion Crete Greece Phone +30 2810 391824 FAX +30 2810 391305 webpage: http://esperia.iesl.forth.gr/˜fthenak **********************************************************
