[Wien] Volume optimization of Sulphur

[Tran, Fabien]

Probably. In case.struct, the lattice constants and angles are for the hexagonal cell, while atoms positions are with respect to rhombohedral.


________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of shamik chakrabarti <shamik15041981 at gmail.com>
Sent: Tuesday, March 10, 2020 10:46 AM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] Volume optimization of Sulphur

It may be a clue for solving the above problem;

              In the struct file (as seen in the GUI) a line remains added :   "positions must be specified in rhombohedral coordinates!"

Looking forward to your response eagerly.

with regards,

On Tue, 10 Mar 2020 at 14:51, shamik chakrabarti <shamik15041981 at gmail.com<mailto:shamik15041981 at gmail.com>> wrote:
Dear Prof. Tran,

                  a^2 c Sin 60 is the volume of the rhombohedral cell having lattice parameter a=b & c. I have used the same formula for hexagonal SnS2 and got very good results. I think somehow the printed volume  is almost 1/2.8 th of the actual value needed. I guess it is something related to R_3 crystal system...........

with regards,

On Tue, 10 Mar 2020 at 14:36, Tran, Fabien <fabien.tran at tuwien.ac.at<mailto:fabien.tran at tuwien.ac.at>> wrote:

WIEN2k does the calculations in the primitive unit cell, whose volume is given by :VOL in case.scf

Is a^2 c Sin 60 not the volume of the conventional cell?

You can visualize the primitive and conventional cells of case.struct with xcrysden (press F3 or F4).


________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at<mailto:wien-bounces at zeus.theochem.tuwien.ac.at>> on behalf of shamik chakrabarti <shamik15041981 at gmail.com<mailto:shamik15041981 at gmail.com>>
Sent: Tuesday, March 10, 2020 9:58 AM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] Volume optimization of Sulphur

Dear Wien2k users,

                              I am also certain that I am not doing any mistake in the formula  of Volume=a^2 c Sin 60. However, the V0 printed in the window showing the fitted BM curve is coming much less than that expected from  a^2 c Sin 60 . What could be the cause? Is it related to the space group R_3 (space group no. 148)?

Looking forward to your reply eagerly.

with regards,


On Tue, 10 Mar 2020 at 13:11, shamik chakrabarti <shamik15041981 at gmail.com<mailto:shamik15041981 at gmail.com>> wrote:
Dear Lyudmila Sir,

                         To remove the confusion I am sending the struct file which have been used in our simulation. I have good results as far as the volume optimization curve is concerned. However, while calculating the lattice parameters using the formula V = a^2 c sin60 I got the low value of lattice parameters. My query is
(1) Whether I have done something wrong in the formula itself?
(2) While GGA is better than nlvdw in this case?

with regards,

--
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India


--
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India
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--
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India


--
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India
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