[Wien] Graphite NMR chemical shifts

Robert Laskowski rolask at ihpc.a-star.edu.sg
Mon Mar 10 15:07:14 CET 2014


if you have metalic case use x_nmr -metal, and TEMP fermi method in in2 (for 
TETRA Fermi level is incorrect in weight files), You may play with -kbT obtion 
for x_nmr (temperature smearing). This may help, however, metals are difficult 
to converge. 



On 10 March 2014 PM 6:21:34 Jose Barquera wrote:
> Dear Wien2k users,
> I have calculated NMR chemical shifts for several crystals and I have
> not had any problem but in the case of graphite something is going
> wrong. The chemical shift it is not converging with the number of k
> points. The value of the chemical shift goes up and down and in some
> cases it just explode. For example: with 33 x 33 x 10 k points the
> values is 4896 ppm while with 26 x 26 x 8 k points the value is 44 ppm
> what it is closer to the expected value.
> I had used 120000 (72 x 72 x 22) k points and it still not converge.
> I had notice that depending in the number of k points some times it
> converge to a insulator configuration and sometimes to a metallic one.
> When it converge to an insulator configuration the chemical shift is
> closer to the experimental value.
> I am using PBE functional but I have also try PBEsol and TPSS without
> success.
> Any idea in what could be the problem?
> Thanks
> kind regards
> Jose
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Dr. Robert Laskowski

Senior Scientist, Materials Science & Engineering Department
Institute of High Performance Computing, A*STAR
1 Fusionopolis Way, #16-16, Connexis, Singapore 138632
Tel(Off): +65. 64191493     Fax: +65. 64632536

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