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--- developers:pseudos:psp3_format [2015/02/25 13:38] – Matteo Giantomassi
+++ developers:pseudos:psp3_format [2020/08/10 18:06] (current) – Xavier Gonze
@@ Line 1: / Line 1: @@
+==== Information on the format 3 for pseudopotentials. ====
+(Note: the implementation of format 3 was done by Fr. Detraux).
+The format 3 for ABINIT pseudopotentials allows to use pseudopotentials
+from the table I in the Phys. Rev. B 58, 3641 (1998) paper
+by C. Hartwigsen, S. Goedecker and J. Hutter (HGH). This paper
+presents LDA pseudopotentials for all elements from H to Rn. Some of them
+are even presented twice, because of the possibility to include semi-core
+states. Their accuracy has been demonstrated in the HGH paper, but note
+that the energy cut-off needed to get this high accuracy might be
+larger than the one usually needed for Troullier-Martins or other
+pseudopotentials. So, convergence studies are very important !
+A few lines must be added to the data mentioned in that table,
+and are described in the present file. ABINITv1.5 is able to
+read format 3 pseudopotential files, as well as later versions of ABINIT.
+We will suppose that the user has the HGH table.
+For the description that follows, we will focus on the Sn pseudopotential.
+In the table (p. 3651), one finds:
+   Sn  4  0.605000  4.610912
+.663544  1.648791 -.141974  -.576546
+.745865  0.769355 -.445070
+.103931 0.005057
+.944459  0.225115
+.007066
+These data must be put in the following format to be read by ABINIT
+(this file is also found in the ~abinit/tests/Psps_for_tests directory,
+with the name 50sn.psphgh) :
+    Hartwigsen-Goedecker-Hutter psp for Tin,  from PRB58, 3641 (1998) paper
+  4   980509                     zatom,zion,pspdat
+   1   2    0    2001    0        pspcod,pspxc,lmax,lloc,mmax,r2well
+.605000  4.610912 0         0         0  rloc, c1, c2, c3, c4
+.663544  1.648791 -.141974  -.576546     rs, h11s, h22s, h33s
+.745865  0.769355 -.445070  0            rp, h11p, h22p, h33p
+.103931 0.005057  0                k11p, k22p, k33p
+.944459  0.225115 0         0            rd, h11d, h23d, h33d
+.007066 0         0                k11d, k22d, k33d
+First, the following three lines have been added at the beginning
+of the data from the table :
+     Hartwigsen-Goedecker-Hutter psp for Tin,  from PRB58, 3641 (1998) paper
+  4   980509                     zatom,zion,pspdat
+   1   2    0    2001    0        pspcod,pspxc,lmax,lloc,mmax,r2well
+Similar lines must be added to the data for other elements, 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 second number mentioned
+in the data table (described as 'Zion' in section VI of the paper)
+Line 3 describes:
+    - the format of the pseudopotential (pspcod ; must be 3 for this format);
+    - the XC functional used to generate the pseudopotential (pspxc ; here, must be 1)
+    - the maximal angular momentum of the wavefunctions described
+      in the pseudopotential file
+         lmax=0 if purely local pseudopotential: H, He, Li^sc, Be^sc ;
+         lmax=1 for s and p projectors : Li, B ... Ar, K^sc, Au ;
+         lmax=2 for s, p and d projectors : K, Ca, ... Cs, Ba, Hf^sc ... Pt^sc, Au^sc ... Rn ;
+         lmax=3 for s, p, d and f projectors : Cs^sc, Ba^sc, La^sc ... Lu^sc
+    - lloc has no meaning, and is set to 0
+    - mmax has no meaning, and is set to 2001
+    - the last number can be set to 0 .
+The lines that follow these three lines
+are generated from the data in the table, though the name of the
+element and Zion are not reproduced. Note also that
+each line has to be completed with zeroes, to give the format presented
+at the beginning of the section VI of the HGH paper :
+five columns for the first of these lines,
+then 4 columns for each projector, and 3 columns for the spin-orbit splitting.
+For readability, the meaning of each number has also been added
+in our example pseudopotential file
+(for example, 'rloc, c1, c2, c3, c4' ) but these are NOT read by ABINIT.
+Thus, unlike the zeroes, it is not important to add them to the
+data from the table.
+Inside ABINIT, the pseudopotential with format 1 will be treated by
+the routine psp2in.f, that calls psp2lo.f (local part) and psp2nl.f (non-local part).
+As a matter of numerical accuracy, note that the integral
+of (V(r)+Zion/r) r^2 in psp2lo.f is performed analytically without cut-off.