C SUBROUTINE PREPOT C C System: ClH2 C Functional form: Extended LEPS (London-Erying-Polyani-Sato) C Common name: G1 C C References for the potential parameters and the potential functional form: C Morse Parameters: C Sato Parameters: C Functional form: P. J. Kuntz, E. M. Nemth, J. C. Polanyi, C S. D. Rosner, and C. E. Young C J. Chem. Phys. 44, 1168 (1966) C C PREPOT must be called once before any calls to POT. C The potential parameters are included in the block data subprogram PTPACM. C Coordinates, potential energy, and derivatives are passed C through the common block PT31CM: C COMMON /PT31CM/ R(3), ENERGY, DEDR(3) C The potential energy in the three asymptotic valleys are C stored in the common block PT5COM: C COMMON /PT35CM/ EASYAB, EASYBC, EASYAC C The potential energy in the AB valley, EASYAB, is equal to the potential C energy of the H "infinitely" far from the ClH diatomic, with the C ClH diatomic at its equilibrium configuration. Similarly, the terms C EASYBC and EASYAC represent the H2 and the HCl asymptotic valleys, C respectively. C The other potential parameters are passed through the common blocks C SATOCM and LEPSCM. C All the information passed through the common blocks PT31CM, PT35CM, C SATOCM, and LEPSCM are in hartree atomic units. C C This potential is written such that: C R(1) = R(Cl-H) C R(2) = R(H-H) C R(3) = R(H-Cl) C The classical potential energy is set equal to zero for the Cl C infinitely far from the equilibrium H2 diatomic. C C The flags that indicate what calculations should be carried out in C the potential routine are passed through the common block PT32CM: C /PT32CM/ NSURF, NDER, NFLAG(20) C where: C NSURF - which electronic state should be used. C This option is not used for this potential as only the C ground electronic state is available. C NDER = 0 => no derivatives should be calculated C NDER = 1 => calculate first derivatives C NFLAG - these integer values can be used to flag options C within the potential; in this potential these options C are not used. C The common block IOCOM contains the FORTRAN unit numbers for the C potential output. In this potential IOCOM contains one variable, IPRT, C /PT34CM/ IPRT C C Potential parameters' default settings C Variable Default value C NSURF 0 C NDER 1 C IPRT 6 C C IMPLICIT DOUBLE PRECISION (A-H,O-Z) COMMON /PT31CM/ R(3), ENERGY, DEDR(3) COMMON /PT32CM/ NSURF, NDER, NFLAG(20) COMMON /PT34CM/ IPRT COMMON /PT35CM/ EASYAB, EASYBC, EASYAC COMMON /SATOCM/ DE(3), RE(3), BETA(3), Z(3) COMMON /LEPSCM/ ZPO(3), OP3Z(3), ZP3(3), TZP3(3), TOP3Z(3), * DO4Z(3), B(3) PARAMETER (CKCAL = 627.5095D0) PARAMETER (CANGS = 0.529177106D0) C C Echo the potential parameters C WRITE (IPRT, 100) DE, RE, BETA, Z C 100 FORMAT (/, 2X, T5, 'PREPOT has been called for the ClH2 ', * 'G1 potential', * //, 2X, T5, 'Potential energy surface parameters:', * /, 2X, T5, 'Bond', T46, 'Cl-H', T58, 'H-H', T69, 'H-Cl', * /, 2X, T5, 'Dissociation energies (kcal/mol):', * T44, F10.5, T55, F10.5, T66, F10.5, * /, 2X, T5, 'Equilibrium bond lengths (Angstroms):', * T44, F10.5, T55, F10.5, T66, F10.5, * /, 2X, T5, 'Morse beta parameters (Angstroms**-1):', * T44, F10.5, T55, F10.5, T66, F10.5, * /, 2X, T5, 'Sato parameters:', * T44, F10.5, T55, F10.5, T66, F10.5,/) C DO 10 I = 1,3 C C Convert to atomic units C DE(I) = DE(I)/CKCAL RE(I) = RE(I)/CANGS BETA(I) = BETA(I)*CANGS C C Compute useful constants C ZPO(I) = 1.0D0 + Z(I) OP3Z(I) = 1.0D0 + 3.0D0*Z(I) TOP3Z(I) = 2.0D0*OP3Z(I) ZP3(I) = Z(I) + 3.0D0 TZP3(I) = 2.0D0*ZP3(I) DO4Z(I) = DE(I)/4.0D0/ZPO(I) B(I) = BETA(I)*DO4Z(I)*2.0D0 10 CONTINUE C C Set the values of the classical energy in the three asymptotic valleys C EASYAB = DE(1) EASYBC = DE(2) EASYAC = DE(3) C RETURN END C C***** C SUBROUTINE POT C C System: ABC C Functional form: Extended LEPS (London-Erying-Polyani-Sato) C References: P. J. Kuntz, E. M. Nemth, J. C. Polanyi, S. D. Rosner, C and C. E. Young C J. Chem. Phys. 44, 1168 (1966) C C The potential parameters must be passed through the common blocks C PT31CM, PT35CM, PT32CM, PT34CM, SATOCM, and LEPSCM. C All information passed through the common blocks PT31CM, PT35CM, C SATOCM, and LEPSCM must be in Hartree atomic units. C C For the reaction: A + BC -> AB + C we write: C R(1) = R(A-B) C R(2) = R(B-C) C R(3) = R(C-A) C C NOTE: The potential energy at the reactant asympotote, that is at C A infinitely far from the BC diatomic, BC diatomic at its C equilibrium configuration, is set equal to zero. C IMPLICIT DOUBLE PRECISION (A-H,O-Z) COMMON /PT31CM/ R(3), ENERGY, DEDR(3) COMMON /PT32CM/ NSURF, NDER, NFLAG(20) COMMON /PT34CM/ IPRT COMMON /PT35CM/ EASYAB, EASYBC, EASYAC COMMON /SATOCM/ DE(3), RE(3), BETA(3), Z(3) COMMON /LEPSCM/ ZPO(3), OP3Z(3), ZP3(3), TZP3(3), TOP3Z(3), * DO4Z(3), B(3) DIMENSION X(3), COUL(3), EXCH(3) PARAMETER (R2 = 1.41421356D0) C C Initialize the variable used in the calculation of the energy. C ENERGY = 0.D0 C C Check the values of NSURF and NDER for validity. C IF (NSURF .NE. 0) THEN WRITE (IPRT, 900) NSURF STOP 'POT 1' ENDIF IF (NDER .GT. 1) THEN WRITE (IPRT, 910) NDER STOP 'POT 2' ENDIF C C Compute the energy. C DO 10 I = 1,3 X(I) = EXP(-BETA(I)*(R(I)-RE(I))) COUL(I) = DO4Z(I)*(ZP3(I)*X(I)-TOP3Z(I))*X(I) EXCH(I) = DO4Z(I)*(OP3Z(I)*X(I)-TZP3(I))*X(I) ENERGY = ENERGY + COUL(I) 10 CONTINUE C RAD = SQRT((EXCH(1)-EXCH(2))**2 + (EXCH(2)-EXCH(3))**2 + * (EXCH(3)-EXCH(1))**2) C ENERGY = ENERGY - RAD/R2 + EASYBC C C Compute the derivatives of the energy with respect to the internal C coordinates. C IF (NDER .EQ. 1) THEN S = EXCH(1) + EXCH(2) + EXCH(3) DO 20 I = 1,3 DEDR(I) = B(I)*X(I)*((3.0D0*EXCH(I)-S)/R2* * (OP3Z(I)*X(I)-ZP3(I))/RAD- * ZP3(I)*X(I)+OP3Z(I)) 20 CONTINUE ENDIF C 900 FORMAT(/,2X,T5,'NSURF has been set equal to ',I5, * /,2X,T5,'This value of NSURF is not allowed for this ', * 'potential, ', * /,2X,T5,'only the ground electronic surface, NSURF = 0, ', * 'is available') 910 FORMAT(/, 2X,'POT has been called with NDER = ',I5, * /, 2X, 'This value of NDER is not allowed in this ', * 'version of the potential.') C RETURN END C C***** C BLOCK DATA PTPACM IMPLICIT DOUBLE PRECISION (A-H,O-Z) COMMON /PT32CM/ NSURF, NDER, NFLAG(20) COMMON /PT34CM/ IPRT COMMON /SATOCM/ DE(3), RE(3), BETA(3), Z(3) C C Initialize the flags and the I/O unit numbers for the potential C DATA IPRT /6/ DATA NDER /1/ DATA NFLAG /20*0/ C C Initialize the potential parameters; the energy C parameters are in kcal/mol, and the lengths are in Angstroms. C DATA DE/ 106.447D0, 109.458D0, 106.447D0/ DATA RE/ 1.2732D0, 0.74127D0, 1.2732D0/ DATA BETA/ 1.8674D0, 1.94130D0, 1.8674D0/ DATA Z/ 0.277D0, 0.077D0, 0.277D0/ C END C C*****