[Pw_forum] Calculation of Gibbs free energies

[Torstein Fjermestad]

 Dear all,

 In one of my projects I would need to compute the Gibbs free energies 
 of structures along a reaction path. After looking through the QE 
 webpage, the pw_forum, and the documentation in the quantum espresso 
 installation directory I think I understand the general procedure:

 1. one calculates the phonons
 2. one computes the interatomic Force Constants with the q2r.x program
 3. one uses the matdyn.x to produce input for the F_QHA.x program
 4. with the F_QHA.x program one can compute the Gibbs free energy and 
 other thermodynamical properties.

 (please correct me if I have misunderstood this general procedure)

 The problem is that I have so far only managed to complete step 1, to 
 compute the phonons. I am currently doing test calculations on a water 
 molecule and this is the input file of the phonon calculation:

 phonons of H2O in super cell at Gamma
  &inputph
   outdir='./',
   prefix='h2o',
   amass(1)=1.01,
   amass(2)=16.01,
   fildyn='h2o.dynG',
   trans= .true.
  /
 0.0 0.0 0.0

 I then try to run the q2r.x calculation with the following input:

 test of q2r calculation
 &input
   fildyn='h2o.dynG',
   flfrc='h2o-output-q2r.fc',
   zasr='no'

 This calculation crashes presumably because it expects a file called 
 h2o.dynG0. But from where do I get this file? As far as I can see the 
 phonon calculation only produces the file h2o.dynG, not a h2o.dynG0 
 file.

 I am completely lost at the moment so I would appreciate if anyone 
 could help me with carrying out the q2r calculation correctly.
 
 Thank you very much in advance,

 Yours sincerely,

 Torstein Fjermestad,
 University of Oslo,
 Norway