[Pw_forum] Fwd:NMR of benzene

[Davide Ceresoli]

nlu at mail.ustc.edu.cn wrote:
>> From: "" <nlu at mail.ustc.edu.cn>
>> Reply-To: "" <nlu at mail.ustc.edu.cn>
>> To: pw_forum at pwscf.org
>> Subject: NMR of benzene
>> Date:Fri, 07 Aug 2009 21:22:14 +0800
>>
>> Dear all,
>> I have used GIPAW to calculate NMR of benzene recently. I have two question,
> the
>> first is why the mass of diamond C is 12 in the input file, in the examples of
>> GIPAW, why not 13?
Dear Lu,
     the NMR calculation is done at fixed atomic positions. The
mass of the isotope matters only when computing phonons.

Notice that in the NMR calculation, every nucleus is considered
NMR active (with nuclear spin > 0). In reality, if the sample is
not enriched, one should take into account the natural abundance
of every isotope.

>> The second is something strange happened in my calculation. When I increase the
>> ecutwfc, the shielding tensor of C did not converge:
>> 40ry:43ppm. 50ry:40ppm. 60ry:46ppm. 70ry:55ppm. 80ry:54ppm. 90ry: 43ppm.
>> 100ry:30ppm. 110ry:27ppm. 120ry:39ppm. 130ry:62ppm. 140ry:85ppm.
Your input looks correct, except for an isolated system you don't
need the macroscopic shape correction. Later tonight or tomorrow,
I'll investigate the problem.


Cheers,
     Davide