Anatase(TiO2)

[namit]

Please provide cif file of amorphous anatase, i want to calculate bandstructure of it or its structure

[abhishek77492652]

It is present in the database of VNL-ATK.

[Petr Khomyakov]

You have to import the crystalline TiO2 from the database of the VNL, and then follow the procedure described, e.g., in this tutorial for SiO2, https://docs.quantumwise.com/tutorials/amorphous_structures/amorphous_structures.html. I notice, however, that there is no unique of making an amorphous material in simulations, as well as in experiment, meaning that you may want to consult the literature about different procedures to model amorphous materials.

[namit]

i know the processs of converting but due to shortage of time i asked for the structure if possible please help .In tutorial i can find this script_tio2_amorphous.py. this is rutile i want the same .py file of anatase.

[Petr Khomyakov]

That was provided as an example of using VNL-ATK for generating amorphous structures rather than for making a complete database of amorphous structures. You may look up the literature, or  invest some time in generating the structure. The force-field (FF) calculations are pretty fast. The only potential time-consuming step would be refining the amorphous structure with DFT, but it might be that your FF-derived model structures will be good enough. You would have to verify that by calculating radial distribution function and possibly other quantities that can be compared to experiment or other simulations.

 

[abhishek77492652]

here is the python file of Anatase

[Petr Khomyakov]

This is not a python file, but cif, the file extension is incorrect. It is also a crystalline structure, not amorphous. The anatase (TiO2) crystalline  structure can be directly imported to the Builder from Add->from Database->Search  for anatase TiO2-> Add to Stash.

[namit]

Yes sir, you are right crystalline structure is present in database. I have successfully verified rdf and CN but the DFT process is taking a lot of time it has been running from 2 days,is there any way to calculate this last step quickly, i mean some changes in parameters may help in fast icalculation.

[Petr Khomyakov]

I would need to see the python script. Could you post it here?

[namit]

Actually i doubt on my process of converting into amorphous. Is the procedure for anatase is same as rutile i.e. given in the tutorial.

[Petr Khomyakov]

I guess the general procedure is the same, even so it might differ in some technical details, in principle. Could you be more specific on what kind of doubts you are having, and what the doubts are based on? 

[namit]

Here is the attached DFT python file which is taking time. I have converted the structure in following way -
---> First from the database i have formed super cell of anatase and then repeated 2x2x1 as instructed in the tutorial.
----> Then using ATK classical and MD i have performed heating at 5000k
-----> Then i again calculated the same step but using but this time using   NVT Nose-Hoover Chain type setting the final temperature to 300k
----> Then the DFT calculation using ATK DFT and two MD blocks as instructed and this is the attached script

[Petr Khomyakov]

Could you also attach the log-file related to this DFT calculation? I assume that you are running this job on a cluster, not on your laptop. Otherwise, it may take really a lot of time.

[namit]

I have running this on my laptop. There is not any other resource

[Petr Khomyakov]

As I said if the amorphous TiO2 model structures generated with classical force field give the RDF and CN in agreement with experiment or other simulations, then you may just proceed to DFT calculations for one or several structures along the classical MD trajectory to get the total energies and density of states (DOS).

Note that the DOS describes the electronic structure of any amorphous materials. One cannot calculate the bands as for crystalline materials because the amorphous solid structures are not described with a periodic lattice, as these structures are disordered.