[Pw_forum] example01 errors;conjugate-gradient algorithm;changing code functionals

[Helen]

I have recently downloaded PWscf and I have several questions.

1. I have compiled PWscf and tried to run example01. During the running of 
espresso-3.2/bin/pw.x <si.scf.cg.in>si.scf.cg.out

I obtain the error message 

forrtl: severe (174): SIGSEGV, segmentation fault occurred

Stack trace terminated abnormally.

The output file seems fine but I cannot run the band program (si.bands.out):

from pp_check_file : error # 1

file /home2/helen/tmp/silicon.save not found

Any ideas about what is going wrong?

2. I would like to carry out an ion relax on an Si crystal. I see from INPUT_PW that the method is a quasi-Newton algorithm, is it possible to use a conjugate-gradient algorithm? Is the quasi-Newton algorithm efficient is the initial ion positions are not so close to the equilibrium structure?

3. I am exploring the possibility of running PWscf with modified functionals, specifically modifiying the exchange and correlation energy functionals to include a descreened two-body interaction. Is this possible? Which parts of the code include the functional forms? Which sub routines should be modified?

Thank you for your help,
Dr. Helen Eisenberg
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