MD.VariableCell false means internal geom. optimization with cell parameters fixed and geom. opt. of internal coordinates of atoms only MD.VariableCell true means full geom. optimization (geom. opt. of both internal coordinates of atoms and cell parameters) so when using MD.VariableCell false cell parameters are fixed
2014-07-21 17:06 GMT+04:00 邵德喜 <dxshao...@gmail.com>: > What do you mean full opt here? And I can not understand " full opt. > with this option "true" cell parameters will be the same". > In my opnion, cell parameters will be change with MD.VariableCell being > false in the structual optimazition. > > > 2014-07-21 20:10 GMT+08:00 Максим Арсентьев <ars21031...@gmail.com>: > > When you perform internal optimization with MD.VariableCell false, cell >> parameters are fixed, so if you further perform full opt. with this option >> "true" cell parameters will be the same. So in both these cases cell >> parameters are the same and you should chose the same kgrig_Monkhorst_Pack >> block and Briollin zone will not change when you transfer from internal to >> full geom. optim. >> >> >> 2014-07-21 15:38 GMT+04:00 Kanhao Xue <xuekan...@gmail.com>: >> >> It is strange argument. When the cell parameter changes, the Brillouin >>> zone will change, therefore the Monkhost-Pack K points will change their >>> locations. However, one is just concerned with the rough density of K >>> points in this scheme. Why one cannot use Monkhorst-Pack? >>> >>> >>> On Mon, Jul 21, 2014 at 11:48 AM, 邵德喜 <dxshao...@gmail.com> wrote: >>> >>>> I was told that when MD.VariableCell is setted True, then we can >>>> not use block kgrid_Monkhorst_Pack option . >>>> Thanks very much . >>>> >>>> >>>> 2014-07-21 15:31 GMT+08:00 Максим Арсентьев <ars21031...@gmail.com>: >>>> >>>> You right, you should perform 2 structural relaxations. Before doing >>>>> this do calculations without geom. optim. with different density of >>>>> kpoints >>>>> by "%block kgrid_Monkhorst_Pack" and see convergence of kpoint density on >>>>> forces. This also should be checked for meshcutoff - convergence in forces >>>>> is very important for geom. optim. >>>>> >>>>> >>>>> 2014-07-21 6:59 GMT+04:00 邵德喜 <dxshao...@gmail.com>: >>>>> >>>>> Thanks very much. >>>>>> Do you mean that I should do structual relaxation twice?First with >>>>>> MD.VariableCell >>>>>> False,then with MD.VariableCell True? >>>>>> If I could just do structual relaxation once with MD.VariableCell >>>>>> True? And if " kgrid Monkhorst Pack" option can be reserved at >>>>>> the same time? >>>>>> Yours Sincerely! >>>>>> Dexishao >>>>>> >>>>>> >>>>>> 2014-07-21 4:55 GMT+08:00 Максим Арсентьев <ars21031...@gmail.com>: >>>>>> >>>>>> Dear, Dexi! >>>>>>> >>>>>>> You can vary residual strain by MD.MaxStressTol. >>>>>>> Use CG, relax with MD.VariableCell False first, then input >>>>>>> coordinates obtained to a new file with MD.VariableCell True. >>>>>>> Note you may need to shift some atoms manually before geometry >>>>>>> optimization: if all atoms are in 2D plane, then all of them will >>>>>>> remain in >>>>>>> plane after geom. optim. because z forces are zero, so you need to shift >>>>>>> any atom to unlock z forces and avoid such a false state. >>>>>>> >>>>>>> >>>>>>> 2014-07-20 4:01 GMT+04:00 邵德喜 <dxshao...@gmail.com>: >>>>>>> >>>>>>> Dear everyone: >>>>>>>> I really want to know how to get a structure wuthout strain.For >>>>>>>> example ,Let's consider graphene ,I get the structure from materials >>>>>>>> studio,and use it as initial one for siesta structual relaxation. >>>>>>>> If in the relaxation set some options as follows: >>>>>>>> MD.TypeOfRun CG/Verlet >>>>>>>> MD.VariableCell True >>>>>>>> ... >>>>>>>> At the same time ,I replace " kgrid Monkhorst Pack" option with >>>>>>>> k-grid cutoff. >>>>>>>> When the relaxation is done,I want to ask if the final structure >>>>>>>> after relaxation is >>>>>>>> one structure without strain? >>>>>>>> In general ,how to get a structure without strain is what I care. >>>>>>>> Thanks in advance. >>>>>>>> Dexi Shao >>>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Best wishes, >>>>>>> Maxim Arsent'ev, D.Sc.(Chemistry) >>>>>>> Laboratory of research of nanostructures >>>>>>> Institute of Silicate Chemistry of RAS >>>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> -- >>>>> Best wishes, >>>>> Maxim Arsent'ev, D.Sc.(Chemistry) >>>>> Laboratory of research of nanostructures >>>>> Institute of Silicate Chemistry of RAS >>>>> >>>> >>>> >>> >>> >>> -- >>> >>> Sincerely yours, >>> Kanhao Xue >>> >>> Laboratoire de Réactivité et Chimie des Solides (LRCS) >>> UMR CNRS 7314 >>> Université de Picardie Jules Verne >>> 33 Rue Saint Leu, 80039 Amiens Cedex, France >>> >> >> >> >> -- >> Best wishes, >> Maxim Arsent'ev, D.Sc.(Chemistry) >> Laboratory of research of nanostructures >> Institute of Silicate Chemistry of RAS >> >> >> -- >> Best wishes, >> Maxim Arsent'ev, D.Sc.(Chemistry) >> Laboratory of research of nanostructures >> Institute of Silicate Chemistry of RAS >> >> > -- Best wishes, Maxim Arsent'ev, D.Sc.(Chemistry) Laboratory of research of nanostructures Institute of Silicate Chemistry of RAS
