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 <[email protected]> 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 <[email protected]>: > > 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 <[email protected]>: >> >> 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 <[email protected]>: >>> >>> 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 <[email protected]>: >>>> >>>> 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
