[Pw_forum] nscf restart

[Vi Vo]

Dear All,

I need to run nscf with a kpt-grid 17x17x17.  However, I can only have 24 hrs to 
run, so the job won't be finished in that short time slot.  I will need to 
restart after every 24hrs.  If I use the 'restart' option, one thing I am 
worried is that after the first run, the scf charge density file will be 
overwritten and replaced by nscf charge density file.  When the job is 
restarted, the charge density file saved in previous run and the *.wfc files 
will be read.  Is the continuing nscf calculation still correct?

One other option is that I can look at how many kpts needed for the grid 
17x17x17 by using the kpt list printed out in the output file if 17x17x17 is 
used, then run smaller jobs, each of which, for example, includes the nscf 
calculation of 20 kpts.  However, when I started the job in this way, more kpts 
than those that I specified in the input file were calculated, eg 40kpts instead 
of 20kpts.  I understand the code searched for other equivalent kpts and 
calculate them.  Because of this, the job required longer time to finish all 40 
kpts than the time I plan.  In order to avoid this, I specified the option 
"nosym=.true.", so that only those kpts I specify in the input file are 
calculated.  However, I am not sure if it is correct to do in this way.  Another 
point encountered is that by chopping into smaller jobs, the kpt weight in each 
20kpts-job is not correct anymore due to the way the code compute the kpt 
weight.  Could you give an advise if there is anything wrong on way I described 
above?

Thank you very much,

Vi
University of Houston      
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