$ECP group            (required if PP=READ in $CONTRL)
 
    This group lets you read in effective core potentials,
for some or all of the atoms in the molecule.  You can use
built in potentials for some of the atoms if you like.
This is a free format (positional) input group.  Since the
input is a little tricky, it is good to look at the two
examples at the end of this group.
 
*** Give a card set -1-, -2-, and -3- for each atom ***
 
-card 1-    PNAME, PTYPE, IZCORE, LMAX+1
 
PNAME is a 8 character descriptive tag for this potential.
 
      If PNAME is repeated later, for the same type of
      element, the previously defined potential is copied
      to this atom.  No other information should be given
      on this card, and cards -2- and -3- must be skipped.
 
      Do not use this "copy" option when there is no core
      potential, instead type "NONE" over and over again.
 
PTYPE = GEN    a general potential should be read.
      = SBKJC  look up the Stevens/Basch/Krauss/Jasien/
               Cundari potential for this type of atom.
      = HW     look up the Hay/Wadt built in potential
               for this type of atom.
      = NONE   treat all electrons on this atom.
IZCORE is the number of core electrons to be removed.
       Obviously IZCORE must be an even number, or in other
       words, all core orbitals being removed must be
       completely occupied.
LMAX+1 is the one higher than the maximum angular momentum
       occupied in the core orbitals being removed:
          to remove s,p,d,f core orbitals  (LMAX=0,1,2,3)
          we use p,d,f,g core potentials (LMAX+1=1,2,3,4).
       LMAX+1 is not permitted to exceed 4.
 
    *** Give IZCORE and LMAX only if PTYPE is GEN ***
 
*** For the first occurrence of PNAME, if PTYPE is GEN, ***
*** then give cards -2- and -3-.  Otherwise go to -1-.  ***
 
*** Card sets -2- and -3- are repeated LMAX+1 times     ***
 
    The potential U(LMAX+1) is given first, followed by
    difference potentials U(L)-U(LMAX+1), for L=0,LMAX.
    Note that is a minus sign, not a hyphen!
    The LMAX potential, and the differences of potentials
    are expanded by Gaussians, on these two cards.
 
-card 2-    NGPOT
 
NGPOT is the number of Gaussians in this part of the
      fit to the local effective potential.
 
-card 3-    CLP,NLP,ZLP   (repeat this card NGPOT times)
 
CLP is the coefficient of this Gaussian in the potential.
NLP is the power of r for this Gaussian, 0 <= NLP <= 3.
ZLP is the exponent of this Gaussian.
 
Note that PTYPE lets you to type in one or more atoms
explicitly, while using built in data for other atoms.
 
By far the easiest way to use the SBKJC potential for all
atoms in the formic acid molecule is to request PP=SBKJC in
$CONTRL.  But here we show two alternatives.  Note that
both examples copy one oxygen potential to the other, and
both explicitly declare there is no potential on every
hydrogen.
 
Assume that the atoms in $DATA are generated in the order
C, H, O, O, H.
 
The first way is to look up the program's internally stored
SBKJC potentials one atom at a time:
 
 $ECP
C-ECP SBKJC
H-ECP NONE
O-ECP SBKJC
O-ECP
H-ECP NONE
 $END
 
The second oxygen duplicates the first, no core electrons
are removed on hydrogen.  The order of the atoms must
follow that generated by $DATA.  All atoms must be given
here in $ECP, not just the symmetry unique atoms.
 
The second example reads all SBKJC potentials explicitly:
 
 $ECP
C-ECP GEN 2 1
1      ----- CARBON U(P) -----
 -0.89371  1  8.56468
2      ----- CARBON U(S)-U(P) -----
  1.92926  0  2.81497
 14.88199  2  8.11296
H-ECP NONE
O-ECP GEN 2 1
1      ----- OXYGEN U(P) -----
 -0.92550  1 16.11718
2      ----- OXYGEN U(S)-U(P) -----
  1.96069  0  5.05348
 29.13442  2 15.95333
O-ECP
H-ECP NONE
 $END
 
Again, the 2nd oxygen copies from the first.  It is handy
to use the rest of card -2- as a descriptive comment.
 
As a final example, for antimony we have LMAX+1=3 (the core
3d is removed, so LMAX=2).  One must first enter U(f),
followed by U(s)-U(f), U(p)-U(f), U(d)-U(f).
 
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