quantum-espresso/examples/example02

This example illustrates how to use pw.x and ph.x to calculate phonon
frequencies at Gamma and X for Si and C in the diamond structure and 
for fcc-Ni.

The calculation proceeds as follows (for the meaning of the cited input
variables see the appropriate INPUT_* file)

1) make a self-consistent calculation (input=si.scf.in,
   output=si.scf.out)

2) make a phonon calculation for gamma point (input=si.phG.in,
   output=si.phG.out). Note that outdir and prefix have the same
   values as in the input for scf calculation.
   Note that the q-point (the Gamma point in this case) is read
   after the namelist inputph. 
   Dynamical matrix will be saved for further analysis in fildyn (whose
   default name is 'matdyn', here overwritten to si.dynG)

   The Gamma point is the ONLY one for which the phonon code can be run
   directly after the scf run (provided save file was defined).
   For all other points in the BZ a non-scf preparatory run is needed,
   as it is shown here for the X point.

3) make a non-scf calculation for X point (input=si.nscfX.in,
   output=si.nscfX.out).
   Note in the input that the same outdir and prefix are given, and
   calculation='phonon' is defined. Note that the previous output file
   that is present in outdir will be overwritten... you could rename
   it if you prefer. Note the q-point for phonon calculation (X point
   in this case) in the namelist "phonon".

4) make a phonon calculation for X point (input=si.phX.in,
   output=si.phX.out). Note that outdir and prefix have the same
   values as in the input of the non-scf run.
   Note that the q-point (the X point in this case) is read after
   the namelist inputph.
   Dynamical matrices will be saved for further analysis in fildyn
   (whose default name is 'matdyn', here overwritten to si.dynX). 
   The fildyn file contains the dynamical matrices for q-points that
   are equivalent by symmetry to the q-point given in input (in this
   case the three X points), therefore when calculating phonons in the
   whole BZ the code needs to be run only on inequivalent points.

   The phonon code can perform also a 'single-mode' calculation where
   only a single atom is moved in a single direction and the corresponding
   column of the dynamical matrix is calculated. This may be useful when
   studying vibrational properties of defects and/or surfaces.
   This feature is illustrated in the last part of the test.

5) make a non-scf calculation at X point for a single mode
   (input=si.nscfXsingle.in, output=si.nscfXsingle.out).
   Note that the same outdir and prefix are given, calculation is set
   to 'phonon', modenum is set to 3 (corresponding to a displacement in
   the z direction of the first atom) are defined. Note that the previous 
   output file that is present in outdir will be overwritten... you could 
   rename. Note the q-point for phonon calculation (X point
   in this case) in the namelist "phonon".

6) make a phonon calculation at X point for a single mode
   (input=si.phXsingle.in, output=si.phXsingle.out). 
   Note that outdir and prefix have the same values as in the input
   for the non-scf run. Note that the q-point
   (the X point in this case) is read after the namelist inputph.  
   The input is identical to case 4), the only difference is that 
   fildyn is given a different name, the default one, in order not to
   overwrite the previous files. The total dynamical matrix is not
   computed and matdyn is actually left empty.

7) make a scf calculation of C (described with US-PP) in the diamond
   structure. 
   (input=c.scf.in, output=c.scf.out).

8) make a phonon calculation at Gamma point for C in the diamond structure. 
   Note that epsil=.true. and the response to an electric field and 
   the dielectric constant are also calculated.
   (input=c.phG.in, output=c.phG.out).

9) make a scf calculation at of magnetic fcc-Ni.
   (input=ni.scf.in, output=ni.scf.out).

10) make a non-scf calculation at X point for magnetic fcc-Ni.
   (input=ni.nscf.in, output=ni.nscf.out). 

11) make a phonon calculations at X point for magnetic fcc-Ni.
   (input=ni.phX.in, output=ni.phX.out).