SUBROUTINE DiatomicPES_SplineFit(r,vpot, vpotp, vpotpp)
USE Numeric_Kinds_Module
USE Numbers_Module
IMPLICIT NONE
SAVE
LOGICAL, PARAMETER :: DBug=.True.
LOGICAL  FirstCall/.True./
CHARACTER(LEN=200), PARAMETER :: FileLoc='D:\Input_Data\Diatomic\H2_CollinearConstantRho\DiatomicPES_SplineFit_Plt.csv'
INTEGER, PARAMETER :: NPoints=601, Pot_File_Unit=635, IOP(2)=(/5,5/)
INTEGER IPoint
REAL(KIND=WP_Kind) r, vpot, vpotp, vpotpp, v2,v3,v6,v20
REAL(KIND=WP_Kind) X(NPoints), PotVal(NPoints), W(NPoints), AT(NPoints), BT(NPoints), CT(NPoints), TAB(3)

IF(FirstCall)THEN
  OPEN(UNIT=Pot_File_Unit, FILE=TRIM(FileLoc))
  READ(Pot_File_Unit,*)
  DO IPoint=1,NPoints
     READ(Pot_File_Unit,'(1PE14.6,2x,1PE14.6,2x,1PE14.6,2x,1PE14.6,2x,1PE14.6)')X(IPoint),PotVal(IPoint), v2,v3, v20
     IF(DBug)WRITE(*,*)X(IPoint), PotVal(IPoint)
  ENDDO
  CLOSE(UNIT=Pot_File_Unit)
  OPEN(UNIT=6,FILE='E:\ParkerE\APH3D\H3\APH3D_H3_PKH3\GraphicsOut\CollinearFixedRhoOut.csv')
ENDIF

IF(r<X(1) .or. r>X(NPoints))THEN
   WRITE(*,*)'ERROR: (r<X(1).or.r>X(NPoints):', r, X(1), X(NPoints)
ENDIF

IF(FirstCall)THEN
  CALL spl1d1(NPoints, X, PotVal, W, IOP, 1, AT, BT, CT)
  FirstCall=.false.
ENDIF

CALL spl1d2(NPoints, X, PotVal, W, 1, r, TAB)
vpot  =TAB(1)
vpotp =TAB(2)
vpotpp=TAB(3)

IF(DBug)THEN
   WRITE(6,'(4(E15.7,","))')r, vpot, vpotp, vpotpp
ENDIF


RETURN
ENDSUBROUTINE DiatomicPES_SplineFit