Nidhi: if you are only interested in the E(a) curve, why are you doing MD annealing? You only need a sequence of ~10 static calculations
MD.TypeOfRun CG # Default value MD.NumCGsteps 0 (the TypeOfRun does not really matter, but you do not need more than the initial step in whatever kind of MD!) for values of lattice constants within several % around the equilibrium, then you fit the results (total energy) to the Murnaghan (or other) equation of state and you get bulk modulus and its derivative immediately from the fit. If you don't have your favourite fitting progran use mine, http://www.home.uni-osnabrueck.de/apostnik/Software/mur_fit.f (have a look at the fitting curve vs. your data points before believing in the numbers you get from the fit!) The interval of A= 5 to 7 Ang might be OK to localize the minimum, but for a clean fit you'd need much more densely situated points just around the minimum. Good luck, Andrei +-- Dr. Andrei Postnikov ---- Tel. +33-387315873 ----- mobile +33-666784053 ---+ | Paul Verlaine University - Institute de Chimie, Physique et Mat\'eriaux, | | Laboratoire de Physique des Milieux Denses, 1 Bd Arago, F-57078 Metz, France | +-- [EMAIL PROTECTED] ------ http://www.home.uni-osnabrueck.de/apostnik/ --+ On Wed, 23 Apr 2008, Nidhi Sharma wrote: | Dear users, | | I am trying to find the Energy vs alat curve for the B1 phase of LaAs. For this I set the MD. type of run Anneal and Target pressure set to 0.0 GPa and vary the value of alat from 5 to 7 Ang in steps of 0.1. | | MD.TypeOfRun Anneal | MD.AnnealOption Pressure | MD.TargetPressure 0.0 GPa | MD.TauRelax 100.0 fs | MD.BulkModulus 100.0 Ry/Bohr**3 | MD.MaxStressTol 0.1 GPa | MD.VariableCell .true. | | I have given default value of Bulk Modulus in .fdf file. What values should I given for MD.BulkModulus in .fdf file. | I got the different energies and pressure for different alat and got the optimal alat. The .out file also report some data in Ry/Bohr**3. I think it is bulk modulus and how we will get the first pressure derivative of Bulk Modulus ? | | Please guide me. | | Thanks in anticipation, | | Nidhi Sharma |
