Only you can answer this, because it depends on what exactly you want to do and what statements you want to make.
For a statement: I've optimized the atomic positions using the exp. lattice parameters, all you need to do is min_lapw For a statement: I've done a full structural optimization, you need to optimize all lattice parameters AND atomic positions simultaneously. Ghosh SUDDHASATTWA schrieb: > Dear Prof.Blaha, > Extending the discussion on internal coordinates minimization and structure > optimization, I have a tetragonal body centered lattice with 58 atoms per > unit cell and 8 inequivalent atoms. > We can use suitable options in the optimization (c/a). Since, the number of > atoms are large enough, can we go in for min_lapw with similar arguments you > mention for monoclinic lattice. > I ask this question as my total run time for SCF (-ec 0.0001 -cc 0.0001 > -in1ef) on 32 cpu's is more than 7 days. > So, is it advisable to do only min_lapw > > I am not asking for any shortcuts, Dear users, > > Suddhasattwa Ghosh > > > > -----Original Message----- > From: wien-bounces at zeus.theochem.tuwien.ac.at > [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha > Sent: Monday, June 28, 2010 12:40 PM > To: A Mailing list for WIEN2k users > Subject: Re: [Wien] FW: Internal Coordinates minimization for Monoclinic > > You are comparing apples and bananas. > > With min_lapw you optimize internal atomic positions, at given (fixed) > lattice > parameters. So you can only say, you have an "optimum structure" with > respect to fixed > (experimental) lattice parameters. > Often, this is a VERY good strategy, since experimental a,b,c are MUCH MORE > accurate > than theoretical ones, while for atomic positions often the opposite holds. > Note, however, you CANNOT use -so for force optimization. > > With the first approach, you can try to find optimal a,b,c,gamma lattice > parameters. However, usually it is also very important to optimize internal > coordinates simultaneously, because this may also influence a,b,c... > As mentioned above, theory is usually quite bad on that and for a monoclinic > structure this gets expensive. > >> I have done the following >> 1. Generate the structure file and run a normal SCF with spin orbit >> coupling. (Since I am working on an heavy element with 18 atoms per unit >> cell) >> 2. Now my question is >> We can either use option 7 and generate 15 structures and optimize the >> structure with minimum energy. >> By modifying the command in optimize.job >> Run_lapw -cc 0.0001 -ec 0.0001 -p -so >> >> Or, we can simply do min_lapw for the structure file we have generated >> initially. >> After running min_lapw, we get the atomic positions with minimum partial >> forces, which gets saved in the structure file. >> Now, using the revised (optimized) atomic coordinates, run a SCF. >> By doing so, can we say that we have the structure with minimum total > energy >> (by doing only min_lapw and not using option 7) >> >> I hope I am clear enough now. >> Thank you >> Suddhasattwa >> >> -----Original Message----- >> From: wien-bounces at zeus.theochem.tuwien.ac.at >> [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha >> Sent: Monday, June 28, 2010 11:02 AM >> To: A Mailing list for WIEN2k users >> Subject: Re: [Wien] FW: Internal Coordinates minimization for Monoclinic >> >> Most likely nobody can answer this question, because nobody understands > your >> question. >> At least I did not understand what you are really doing. >> >> Did you run x optimize with option 7 ? >> Did you modify optimize.job or just run it unmodified ? >> Did you put min_lapw instead or run_lapw ? >> Did you find the structure with lowest total energy ? >> >>> Coming back to my question, doing a 4-D optimization of a monoclinic >>> case by choosing Option 7, can we say with authority that >>> >>> 1. Internal coordinates minimization of monoclinic case (with 18 atoms >>> per unit cell) keeping the lattice parameters same would be enough to >>> know the total energy. >>> >>> In any case, after lapw_mini, the optimized coordinates are saved in the >>> case.struct, so running the SCf again would give the optimized total >>> energy. >> Why would you run again an scf ? You already have one ? >> >> > -- P.Blaha -------------------------------------------------------------------------- Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna Phone: +43-1-58801-15671 FAX: +43-1-58801-15698 Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/ --------------------------------------------------------------------------
