I am going to draw a hexagonal crystal for pure Mg, MgCl2 and solid solution mg phase with Materials studio. But I found some problem in drawing the crystal.
For example for the case of Mg2Ca, I built a P63/mmc(194) crystal. Then I added Mg atoms in (0, 0, 0) locations. 6 atoms appeared in the screen. Then I added Ca atoms in the (0.33, 0.67, 0.062) but it seems that 8 Ca atoms were added which half were overlapped with the rest (see the picture).
I can not understand based on which formula these atoms are added and how can I modify just single atom.
I extracted the location of atoms from this paper.
http://yadda.icm.edu.pl/yadda/element/bwmeta1.element.elsevier-5e87325f-c99e-30af-a496-17eb5db795dc
Kindest Regards
The symmetry operations of the space group P63/mmc map each position onto a list of equivalent positions. These are listed on the space group table entry for the group:
http://img.chem.ucl.ac.uk/sgp/large/194az1.htm
I suspect what's happening in your case is that because you've truncated your atom positions to two significant figures, some of the equivalent positions are not - within the program's threshold - exactly equivalent. For example, if position 1 is (0.33, 0.67, 0.062) then position 8 is (0.34, 0.67, 0.062) which is not EXACTLY the same. Therefore, twice as many atoms are created and they almost overlap. The solution is to specify the atom positions to a greater number of significant figures.
Personally, to create a structure I'm using a very simple and completely free program called VESTA : http://jp-minerals.org/vesta/en/
You can create your exact structure in few minutes (see the picture of your example Mg2Ca)
And after creating your structure with VESTA, export it as a *.cif file and finally import it in Material Studio.
http://jp-minerals.org/vesta/en/
The symmetry operations of the space group P63/mmc map each position onto a list of equivalent positions. These are listed on the space group table entry for the group:
http://img.chem.ucl.ac.uk/sgp/large/194az1.htm
I suspect what's happening in your case is that because you've truncated your atom positions to two significant figures, some of the equivalent positions are not - within the program's threshold - exactly equivalent. For example, if position 1 is (0.33, 0.67, 0.062) then position 8 is (0.34, 0.67, 0.062) which is not EXACTLY the same. Therefore, twice as many atoms are created and they almost overlap. The solution is to specify the atom positions to a greater number of significant figures.
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