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--- developers:pseudos:psp6_format [2015/02/25 13:50] – Matteo Giantomassi
+++ developers:pseudos:psp6_format [2020/08/10 18:04] (current) – Xavier Gonze
@@ Line 1: / Line 1: @@
+==== Information on the format 6 for pseudopotentials ====
+The format 6 for ABINIT pseudopotentials allows to use pseudopotentials
+generated from the FHI98PP code (Fritz-Haber-Institute, Berlin).
+This code is available at URL http://www.FHI-Berlin.MPG.DE/th/fhi98md/fhi98PP .
+A few lines must be added to the file generated by the FHI98PP code,
+and are described in the present file. ABINITv1.9 is able to
+read format 6 pseudopotential files without core correction.
+ABINITv2.2 is able to read them with core correction (thanks to AF).
+) The original cpi file
+We will suppose that the user has been able to generate a 'cpi' filen from the FHI98PP code.
+There is one such file in the ~abinit/tests/Psps_for_tests directory,
+with the name al_h.cpi (the FHI98PP code generated a file named "al:h.cpi", but the name was changed,
+to allow portability under DOS/Windows) .
+It begins by:
+.30000000000000E+01   3
+.0000    0.0000    0.0000   0.0000
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+.0000    .00e+00   .00e+00
+  0.10247000000000E+01
+0.48076923076923E-03 0.91926957204792E-04 0.72762392428392E+00
+0.49264423076923E-03 0.94197553047751E-04 0.72762434262851E+00
+0.50481254326923E-03 0.96524232608030E-04 0.72762477651319E+00
+  ...
+  ...
+From these numbers, we will make direct use of:
+  - those on the first line,i.e. the number of valence electrons (0.30000000000000E+01) and the number of pseudopotential components (3)
+  - the first on the 12th line, i.e. the number of mesh points (493)
+) The new file
+For the purpose of generating the corresponding file readable by ABINIT (also
+found in the ~abinit/tests/Psps_for_tests directory, with the name 13al.981214.fhi),
+the following seven lines have been added at the beginning of the al_h.cpi file:
+  Aluminum, fhi98PP : Hamann-type, LDA CA PerdewWang, l=2 local
+.000  3.000    981214              zatom,zion,pspdat
+       7        2   2    493     0  pspcod,pspxc,lmax,lloc,mmax,r2well
+.0     0.0     0.0                  rchrg, fchrg, qchrg
+--- These two lines are available for giving more information, later
+-Here follows the cpi file from the fhi98pp code-
+Similar lines must be added at the beginning of other cpi files, in order
+to make them readable by ABINIT.
+Line 1 is simply a header, that might include any information, and that will
+be printed without modification in the output of ABINIT.
+Line 2 describes:
+    - the atomic number (zatom);
+    - the ionic charge (zion, number of valence electrons);
+    - the date of pseudopotential generation.
+The two first information are crucial, the third one is not
+really important. The atomic number is 1 for Hydrogen, 8 for Oxygen, and so on.
+The ionic charge should be the same number as the first number mentioned
+in the cpi file (called 'number of valence electrons').
+Line 3 describes:
+  - the format of the pseudopotential (pspcod ; must be 6 for this format);
+  - the XC functional used to generate the pseudopotential (pspxc; the same numbers as for the input variable ixc should be used, see ~abinit/doc/users/abinit_help.html)
+  - the maximal angular momentum of the wavefunctions described in the pseudopotential file (lmax=0 if only s-wavefunctions are present, lmax=1 for s and p wfs, lmax=2 for s, p and d wfs ... ; lmax+1 must be equal to the 'number of pseudopotential components' mentioned in the cpi file, as the second number of the first line)
+  - the angular momentum of the potential to be used as local pseudopotential (lloc=0 if s-potential is local; lloc=1 if p-potential is local; ... )
+  - the number of radial mesh points (mmax, same meaning as in the cpi file; first number on the 12th line)
+  - the last number can be set to 0.
+Line 4 describes 3 parameters needed to read the model core-charge if core correction is needed.
+  - rchrg: radius at which the core charge vanish (i.e. cut-off in a.u.)
+  - fchrg: amplitude of core charge (if =0 non core-correction performed, if >0 core-correction is applied). The specific value of fchrg has no physical meaning in fhi98pp scheme of core correction.
+  - qchrg: integrated model core charge (it's not actually used by abinit, and can be set to any value)
+rchrg can be inferred by the pp file. Indeed, if the pp has been generated
+with the core-correction option, at the end of 'cpi' file there will be:
+     do i=1,mmax
+       rad(i), f(i), f1(i), f2(i)
+     end do
+that is, the radial grid, the core charge (f), and their first(f1)
+and second (f2) derivative on the radial mesh; rchrg can be equal
+to any value of rad(i) to which f,f1 and f2 are reasonably vanished.
+Line 5-7 have no interest up to now.
+A pseudopotential with format 6 will be treated by
+the routine psp6in.f, that calls psp5lo.f (local part) and
+psp5nl.f (non-local part). There is no psp6lo.f or psp6nl.f .
+The integral of (V(r)+Zion/r) r^2 in psp5lo.f is performed
+from 0 to the highest allowed radius (usually about 100 a.u.),
+except that beyond 20 a.u. no value of abs(V(r)) larger
+than 2.0d-8 is tolerated. This will allow to cut off spurious
+behaviour of pseudopotential whose data file is written in single precision.