
The module potential in potential.f90 contains the routines for reading the potential data from 
the file 'potential' and evaluating the potential and derivatives.

The file 'potential' needs to be in the directory where the main program is run. 

See check_pes.f90 for an example of how to call the potential routine.
When check_pes.f90 is compiled and run, it should result in deviations from the data and computed values of ~ 1D-10

In brief:

    call pesdata_init()
    call pes(x,iopt,e,g,h)
    call pesdata_final()

 x(3,natoms)  Cartesian coordiates in bohr - connectivity assumed to be as eq structure
 iopt = 0   evaluate energy only                    : e 
        1   evaluate energy and gradient            : g(3*natoms)
        2   evaluate energy, gradient and hessian   : h(3*natoms*(3*natoms+1)/2)  stored as  (1,1) (2,1) (2,2) (3,1) (3,2) (3,3) ...

CCSD(T)(F12*)/aug-cc-pVTZ equilibrium structure

  o   0.00000000000000     -0.33882571727265      1.34408937808849
  h  -1.44238852025759      0.45256066803026      2.10527109352390
  h   1.44238852025759      0.45256066803026      2.10527109352390
  h   0.00000000000000     -0.32260575753413     -1.89615140576944
  f   0.00000000000000     -0.24368986125373     -3.65848015936685

PES equilibrium structure

  o   0.00000000000000     -0.34022219602750      1.34858112251000
  h  -1.44243120705392      0.45339120403616      2.10689754818247
  h   1.44243120705392      0.45339120403616      2.10689754818247
  h   0.00000000000000     -0.32573833602602     -1.90036056903419
  f   0.00000000000000     -0.24082187601880     -3.66201564984076


CCSD(T)(F12*)/aug-cc-pVTZ C2v structure

  o   0.00000000000000      0.00000000000000      1.22212647624589 
  h  -1.44922677497562      0.00000000000000      2.30583098628091 
  h   1.44922677497562      0.00000000000000      2.30583098628091 
  h   0.00000000000000      0.00000000000000     -2.03716516918317 
  f   0.00000000000000      0.00000000000000     -3.79662327962454 

PES C2V structure        108.3476  cm-1

  o     0.00000000      0.00000000      1.224352024  
  h    -1.44926763      0.00000000      2.307941604  
  h     1.44926763      0.00000000      2.307941604  
  h     0.00000000      0.00000000     -2.040477216  
  f     0.00000000      0.00000000     -3.799758016  

