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 **********************************************************
