Dear all,
I was trying to make POSCAR file of crystalline disordered material Ge2Sb2Te5. I downloaded its cif file from ICSD database, but when i converted it into POSCAR file then it is showing Sb 0 atom. Then how can we run its VASP calculations?
Then i deliberately made Te5Ge2Sb2, but is it the correct way to do the calculations?
Kindly find the attached files for my edited POSCAR and ICSD cif file.
According to your CIF file, there is an occupation of 1/3 for Sb in the 2d Wyckoff position, while there is an occupation of 2/3 in the 2c. So, when you open the CIF file with a program such as VESTA the atoms appear with different colors according to the occupation. Hence, you will have to choose the positions of your atoms according to the occupation and your own criteria. Always you can make several POSCAR and see the stability of each one.
Dear Sir,
Thank you for the valuable information. Can you please elaborate what do you mean by several POSCAR here? How we have to consider different combinations? Should we have to apply AIMD calculations for the stability of the structure?
In above POSCAR, i have taken the combination by my own, like Te5Ge2Sb2 (sorry i didn't mentioned it in above question). But, I don't know, whether it is correct or not?
Thanks in advance!
Dear Sir,
Thank you for your answer. I have used this tool and got the following file with the composition Ge4Sb4Te5 where Ge and Sb have same coordinate positions. Kindly let me know whether it is correct or not?
I would be very thankful to you for the same.
A disordered material is, as the name implies, disordered. On the average in the entire crystal the atoms occupy a fraction of each position in the unit cell. By placing the atoms at each position of a POSCAR file and applying periodic boundary conditions you force the crystal to be ordered.
One way to deal with a disordered material is to use special quasirandom structures (SQS). They can be created using the ATAT package which attempts to generate an ordered crystal that is sufficiently disordered to represent the disordered materials.
Here is some literature you may want to look at: Article Electronic properties of random alloys: Special quasirandom structures
Article Special quasirandom structures
Article Efficient stochastic generation of special quasirandom structures
Dear Sir,
Thank you for the valuable information. I will look into it.
Thanks!
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