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About MD.Fixed.XYZ Date: 2016/06/18 02:36 Name: Guilherme Maia   <guisawyer@yahoo.com.br> Dear OpenMX authors and users, I'm having a kind problem with the MD.Fixed.XYZ... let's suppose that I have one system with 2 atoms, in the positions: X Y Z 1 Atom1 0.0 0.0 0.23 2 Atom2 0.5 0.0 0.23 and I want only do the constrained relaxation only in the z-coordinate! So I have to do: <Md.Fixed.XYZ 1 1 1 0 2 1 1 0 MD.Fixed.XYZ> But the problem is the relaxation has to be the same to the both atoms!! But in the end of simulation I obtained something like: 1 Atom1 0.0 0.0 0.29 2 Atom2 0.5 0.0 0.17 Its possible create some kind of link?! So.. in the end I find something like: 1 Atom1 0.0 0.0 0.27 2 Atom2 0.5 0.0 0.27 Thanks Best Regards!

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Re: About MD.Fixed.XYZ ( No.1 ) Date: 2016/06/23 13:50 Name: T. Ozaki Hi, Please provide more information. Otherwise, it is difficult to figure out what happened in your calculation. Regards, TO Re: About MD.Fixed.XYZ ( No.2 ) Date: 2016/06/26 05:35 Name: Guilherme Maia  <guisawyer@yahoo.com.br> Hi T. Ozaki, Ok, I'll try explain what is happening... I started to do the study of the PTO (PbTiO3) Space group name P 4 m m Space group number 99 and the Wyckoff Positions only allowed me to relax in the z-coordinate! To keep the symmetry!! (Ref http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list ) The unit cell of the PTO are: 1 Pb Pb1 0.00000 0.00000 0.00000 2 Ti Ti1 0.50000 0.50000 0.52810 3 O O1 0.50000 0.00000 0.61300 4 O O2 0.50000 0.50000 0.13390 But to do the Simulation I can't use only the unit cell... I have to specify more atoms, in this case: 1 Pb Pb1 0.000000000 0.000000000 0.000000 2 Ti Ti1 0.500000000 0.500000000 0.528100 3 O O1 0.500000000 0.000000000 0.613900 4 O O1 0.000000000 0.500000000 0.613900 5 O O2 0.500000000 0.500000000 0.133900 So the Atom 3 and 4 have to move the same distance to keep the symmetry... I had check the out of the file.dat# and the Atom 3 and 4 don't appear with the same.. but was almost the same.. I think I'm being too hard on it. the difference its very small... The position after : 1 Pb 0.00000000000000 0.00000000000000 0.03315150938798 7.0 7.0 2 Ti 0.50000000000000 0.50000000000000 0.54504033072155 6.0 6.0 3 O 0.50000000000000 0.00000000000000 0.60553117155627 3.0 3.0 4 O 0.00000000000000 0.50000000000000 0.60553199091178 3.0 3.0 5 O 0.50000000000000 0.50000000000000 0.09935469249243 3.0 3.0 the z-coordinate of the atoms 3 e 4 I can say are the same!!! So, its OK!! But, have some kind of option that make in this case, the atoms 3 and 4 move exactly the same?! I hope its clear now!! Best Regards!

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