$TESCAV group                              (optional)
 
    This group controls the tessellation procedure for the
cavity surfaces in PCM computations.  The default values
for this group will normally be satisfactory.  Use of the
FIXPVA mechanism for dividing the surface of the atomic
spheres into tesserae should allow for convergent PCM
geometry optimizations.  To converge to small OPTTOL values
may require the use of internal coordinates, since the
tessellation amounts to a finite grid (so the PCM energy is
not strictly rotationally invariant).
 
   Cartesian geometry optimizations may require a high
density of tesserae on the cavity surface:
    NTSALL=240   (or 960)
This may require raising the maximum number of tesserae,
see MXTS in $PCM.  It is reasonable to just try internal
coordinates first, as this should be sufficient w/o
increasing the tesserae density.  See also IFAST=1 in
$PCMGRD.
 
--- The first two arrays control the density of tesserae
and the method to generate the tesserae.
 
INITS  =  array defines the initial number of tesserae for
          each sphere. Only 60, 240 and 960 are allowed,
          but the value can be different for each sphere.
          (Default is INITS(1)=60,60,60,...)  See NTSALL.
 
METHOD =  array defining the tessellation method for each
          sphere.  The value can be different for each
          sphere.  The default is 4 for all spheres, e.g.
          METHOD(1)=4,4,4,...  See also MTHALL.
       =  1  GEPOL-GB, "Gauss-Bonet" tessellation.
       =  2  GEPOL-AS, "area scaling" tessellation.
       =  3  GEPOL-RT, "regular tessellation".
       =  4  FIXPVA, "Fixed points with variable area".
FIXPVA gives smooth potential surfaces during geometry
optimizations, works with $PCM options ICAV and IDISP (but
not with IDP or IRP), and is the preferred tessellation
method.
 
--- The next three parameters are presets for filling the
    arrays INITS and METHOD with identical values.
 
NTSALL =  60, 240 or 960 (default = 60)
          All values in the array INITS are set to NTSALL
 
MTHALL =  1, 2, 3, or 4 (default = 4)
          All values in the array METHOD are set to MTHALL
 
MTHAUT =  0 or 1 (default = 0)
          If RUNTYP=OPTIMIZE and frozen atoms are defined
          by IFCART, MTHAUT=1 will select METHOD=1 for
          frozen atoms. See also AUTFRE and NTSFRZ.
 
note: Explicitly defining INITS and METHOD from the input
      deck will overrule the presets from NTSALL, MTHALL
      and/or MTHAUT.
 
--- The following two parameters control GEPOL-RT
 
AREATL =  The area criterion (A*A) for GEPOL-RT.
          Tesserae with areas < AREATL at the boundary of
          intersecting spheres will be neglected.
          Default=0.010 A*A. Smaller AREATL cause larger
          number of tesserae.  AREATL < 0.00010 is not
          recommended.
 
BONDRY =  Controls (by scaling) the distance within which
          tesserae are considered "close" to the boundary.
          Such tesserae will be recursively divided into
          smaller ones until their areas are < AREATL.
          The default (= 1.0) means the distance is the
          square root of the tessera area.
          A large BONDRY value like 1000.0 will lead to
          fine tessellation for the entire surface with
          all tessera areas < AREATL.
 
--- The next two parameters are only relevant if MTHAUT=1
 
AUTFRE =  Distance (A) for frozen atoms to be treated as
          moving atoms when MTHAUT=1. Default=2.0 A.
 
NTSFRZ =  60, 240 OR 960, initial tessera number for
          frozen atoms. Default=60
 
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