[Wien] nlvdw for SnS2

[Tran, Fabien]

First thing: It is a very bad idea to combine PBEsol with the NL-vdW kernel corresponding to type=1 and Zab=-1.887, because the lattice constants will be probably clearly too short. Only the NL-vdW kernel rVV10s (see Sec. 4.5.14 of the WIEN2k UG) should be combined with PBEsol, but I still would not use PBEsol+rVV10s because it is not so good (see https://doi.org/10.1103/PhysRevMaterials.3.063602).<https://doi.org/10.1103/PhysRevMaterials.3.063602> Better functionals like rev-vdW-DF2 or vdW-DF-cx should be used.


(1) Since the layers in SnS2 are weakly bound, I would use SCAN+rVV10. How to use SCAN+rVV10 is explained in Secs. 4.5.14 and 7.3.2 of the UG: the 1st and 2dn lines of case.innlvdw are

2                     kernel type

15.7 0.0093   parameters of the kernel


(2) What do you mean by "but nothing happens."? is the module nlvdw not running at all?


________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of shamik chakrabarti <shamik15041981 at gmail.com>
Sent: Sunday, February 2, 2020 3:39 PM
To: A Mailing list for WIEN2k users
Subject: [Wien] nlvdw for SnS2

Dear Wien2k users,

                          I have done structural optimization (volume & then c/a & then force) with nlvdw without any problem. I have used Rmt*Kmax=9 and Gmax=25. The case.innlvdw and case.in0 are as follows;

case.innlvdw

1              kernel type
-1.887        parameters of the kernel
25             plane-wave expansion cutoff GMAX
0.3            density cutoff rhoc
T              calculation of the potential (T or F)
10             plane-wave expansion cutoff GMAXpot for the potential

case.in0

TOT  XC_PBESOL     (XC_LDA,XC_PBESOL,XC_WC,XC_MBJ,XC_SCAN)
NR2V      IFFT      (R2V)
   54   54   90    2.00  1 NCON 9  # min IFFT-parameters, enhancement factor, iprint, NCON n

However, after optimization of lattice parameters & atomic coordinates, I have tried to simulate energies using SCAN meta-GGA. But in this case I got confused about proper input parameters as stated below:

(1) What will be the format of case.innlvdw  (Do we need to use scan+rVV10? if yes we have to use kernel type 2 but how? how to set b & c parameter in case.innlvdw?)

(2)  After setting all the parameters when I tried to run runsp_lapw -nlvdw....using commandline in gui I have been directed to run scf window where I was not able to find the -nlvdw switch and if I start run scf...the simulation starts with runsp_lapw without -nlvdw switch...? I have also tried to set the commands in terminal but nothing happens.

Looking forward to your suggestions eagerly. Thanks in advance

with regards,


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