Dear Bhamu, There is an alternative way. You may use the OrthoOpt package available at http://susi.theochem.tuwien.ac.at/reg_user/unsupported/OrthoOpt/ It proceeds in a similar way Stefaan has suggested in previous mail copied below. It first fixes the volume and finds a minimum energy depending on two variables: c/a and b/a. Then, it moves to the next volume and so on until it reaches minimum volume. HTH Tomas
No, not really. You have three (unit cell) degrees of freedom: E(a,b,c). Or similarly E(V, b/a, c/a) (with V=a*b*c). The different options in optimize_lapw give you a series of unit cells with either different values of V (and b/a and c/a constant), different values of b/a (and V and c/a constant) and different values of c/a (and V and b/a constant). These are three slices through the energy landscape. By finding the energy minimum along one slice, fix it, then go on with the next slice, etc. … you can gradually approach the absolute energy minimum. It might take several iterations through this scheme if your starting cell is far away from the minimum. Best is to start first with the degree of freedom that affects energy most (usually the volume). Stefaan Předmět: Re: [Wien] optimization of an orthorhombic cell Dear List, Could you please help me to get optimize lattice parameters from the procedure that I followed as mentioned below: The procedure is a four-step task what I am following: The original lattice parameters were: a, b, c=16.763005, 24.803600, 16.320431 vol 6785.64777697697 bohr^3. 1. VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice) getting below optimized data: ========================================================== Lowest point on X-axis is = -1.615800 Minimum value of B/A is = 1.455755 Minimum value of ENE is = -339059.104498 Ry ========================================================== Value of A is = 16.85428 bohr ; 8.91890 Ang Value of B is = 24.53569 bohr ; 12.98373 Ang Value of C is = 16.40929 bohr ; 8.68342 Ang ========================================================== Initial value of B/A is = 1.479663 Conv. Unit Cell Vol = 6785.7557 bohr^3 ; **********Ang^ 2. Volume optimization using option 1 in "x optimize" and then calculating new volume from eplot option. Query: Step two is giving optimized volume but I do not know how to calculate lattices parameters from a single volume value for the next step "VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice)"? The original cell volume and lattice parameters are mentioned at the beginning. and the new volume from step two is: 6815.3427 bohr^3 The above same query is for the remaining process: 3. optimization of C/A 4. optimization of V. *5 At the final step I will do structural relaxation (min_.....). Could you please advice me how to proceed? Kind regards, Bhamu _______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
