Gaussian Z-Matrices



 Hi Netters!
 	My evil boss gave me the assignment of calculating points
 with Gaussian 94, but I don't have the manual!  I created the
 Z matrix for CH4 and NH3 on my own and ran them.  Here is a
 listing of the partial output:
 For CH4 I got --
  **************************************************
  Gaussian 94:  CrayXMP-Unicos-G94RevD.3  1-May-1996
                     22-Jul-1996
  **************************************************
  %chk=ch4
  -----------------
  #RHF/6-31G** Test
  -----------------
  1/38=1/1;
  2/12=2,17=6,18=5/2;
  3/5=1,6=6,7=101,11=1,25=1,30=1/1,2,3;
  4/7=1/1;
  5/5=2,32=1,38=4/2;
  6/7=2,8=2,9=2,10=2,19=1,28=1/1;
  99/5=1,9=1/99;
  ----------------------------
  Single point CH4 calculation
  ----------------------------
  Symbolic Z-matrix:
     Charge = 0 Multiplicity = 1
  C
  H     1     RCH1
  H     1     RCH2      2     DTET
  H     1     RCH3      2     DTET      3     DIHE      0
  H     1     RCH4      2     DTET      3     -DIHE     0
        Variables:
   RCH1                  1.
   RCH2                  1.
   RCH3                  1.
   RCH4                  1.25
   DIHE                120.
   DTET                109.5
  ------------------------------------------------------------------------
                          Z-MATRIX (ANGSTROMS AND DEGREES)
  CD Cent Atom  N1     Length/X     N2    Alpha/Y     N3     Beta/Z      J
  ------------------------------------------------------------------------
    1   1  C
    2   2  H     1   1.000000(  1)
    3   3  H     1   1.000000(  2)   2  109.500(  5)
    4   4  H     1   1.000000(  3)   2  109.500(  6)   3  120.000(  8)   0
    5   5  H     1   1.250000(  4)   2  109.500(  7)   3 -120.000(  9)   0
  ------------------------------------------------------------------------
                   Z-Matrix orientation:
  ----------------------------------------------------------
  Center     Atomic              Coordinates (Angstroms)
  Number     Number             X           Y           Z
  ----------------------------------------------------------
     1          6           0.000000    0.000000    0.000000
     2          1           0.000000    0.000000    1.000000
     3          1           0.942641    0.000000   -0.333807
     4          1          -0.471321   -0.816351   -0.333807
     5          1          -0.589151    1.020439   -0.417259
  ----------------------------------------------------------
                     Distance matrix (angstroms):
               1          2          3          4          5
   1  C    0.000000
   2  H    1.000000   0.000000
   3  H    1.000000   1.633283   0.000000
   4  H    1.000000   1.633283   1.632703   0.000000
   5  H    1.250000   1.843100   1.842457   1.842457   0.000000
                            Interatomic angles:
        H2-C1-H3=109.5          H2-C1-H4=109.5          H3-C1-H4=109.4424
        H2-C1-H5=109.5          H3-C1-H5=109.4424       H4-C1-H5=109.4424
  Stoichiometry    CH4
  Framework group  CS[SG(CH2),X(H2)]
  Deg. of freedom    6
  Full point group                 CS      NOp   2
  Largest Abelian subgroup         CS      NOp   2
  Largest concise Abelian subgroup CS      NOp   2
                    Standard orientation:
  ----------------------------------------------------------
  Center     Atomic              Coordinates (Angstroms)
  Number     Number             X           Y           Z
  ----------------------------------------------------------
     1          6           0.000000    0.025048    0.000000
     2          1           0.940843    0.363889    0.000000
     3          1          -0.473763    0.355379    0.816351
     4          1          -0.473763    0.355379   -0.816351
     5          1           0.006683   -1.224934    0.000000
  ----------------------------------------------------------
 And, for NH3 I got --
  **************************************************
  Gaussian 94:  CrayXMP-Unicos-G94RevD.3  1-May-1996
                     30-Jun-1996
  **************************************************
  %chk=nh3
  -----------------
  #RHF/6-31G** Test
  -----------------
  1/38=1/1;
  2/12=2,17=6,18=5/2;
  3/5=1,6=6,7=101,11=1,25=1,30=1/1,2,3;
  4/7=1/1;
  5/5=2,32=1,38=4/2;
  6/7=2,8=2,9=2,10=2,19=1,28=1/1;
  99/5=1,9=1/99;
  ----------------------------
  Single point NH3 calculation
  ----------------------------
  Symbolic Z-matrix:
     Charge = 0 Multiplicity = 1
  N
  X1    N     RX
  H1    N     RNH       X1    DUMB
  H2    N     RNH       X1    DUMB      H1    DIHE      0
  H3    N     RNH       X1    DUMB      H1    -DIHE     0
        Variables:
   RX                    1.02
   RNH                   1.02
   DIHE                120.
   DUMB                108.
  ------------------------------------------------------------------------
                          Z-MATRIX (ANGSTROMS AND DEGREES)
  CD Cent Atom  N1     Length/X     N2    Alpha/Y     N3     Beta/Z      J
  ------------------------------------------------------------------------
    1   1  N
    2      X     1   1.020000(  1)
    3   2  H     1   1.020000(  2)   2  108.000(  5)
    4   3  H     1   1.020000(  3)   2  108.000(  6)   3  120.000(  8)   0
    5   4  H     1   1.020000(  4)   2  108.000(  7)   3 -120.000(  9)   0
  ------------------------------------------------------------------------
                   Z-Matrix orientation:
  ----------------------------------------------------------
  Center     Atomic              Coordinates (Angstroms)
  Number     Number             X           Y           Z
  ----------------------------------------------------------
     1          7           0.000000    0.000000    0.000000
     2         -1           0.000000    0.000000    1.020000
     3          1           0.970078    0.000000   -0.315197
     4          1          -0.485039   -0.840112   -0.315197
     5          1          -0.485039    0.840112   -0.315197
  ----------------------------------------------------------
                     Distance matrix (angstroms):
               1          2          3          4          5
   1  N    0.000000
   2  X    1.020000   0.000000
   3  H    1.020000   1.650395   0.000000
   4  H    1.020000   1.650395   1.680224   0.000000
   5  H    1.020000   1.650395   1.680224   1.680224   0.000000
                            Interatomic angles:
        X2-N1-H3=108.           X2-N1-H4=108.           H3-N1-H4=110.9015
        X2-N1-H5=108.           H3-N1-H5=110.9015       H4-N1-H5=110.9015
  Stoichiometry    H3N
  Framework group  C3V[C3(N),3SGV(H)]
  Deg. of freedom    2
  Full point group                 C3V     NOp   6
  Largest Abelian subgroup         CS      NOp   2
  Largest concise Abelian subgroup CS      NOp   2
                    Standard orientation:
  ----------------------------------------------------------
  Center     Atomic              Coordinates (Angstroms)
  Number     Number             X           Y           Z
  ----------------------------------------------------------
     1          7           0.000000    0.000000    0.094559
     2          1           0.000000    0.970078   -0.220638
     3          1           0.840112   -0.485039   -0.220638
     4          1          -0.840112   -0.485039   -0.220638
  ----------------------------------------------------------
 I have two questions about these:
 (1)  First, how do I change the input so I can run multiple
 geometries at once?  For example, I would like to change
 a bond length from 0.8 Angstroms to 1.6 Angstroms in increments
 of 0.1 Angstroms?
 (2)  I ran these SYMMETRIC cases for CH4 and NH3 to see if
 my input deck was correct?  But, I was surprised to see that
 when Gaussian 94 calculated the Interatomic angles they didn't
 have the symmetry I expected.  Notice in NH3 that the H-N-H
 bond angles are not 111 degrees like I had expected.
 Am I misunderstanding this?
 Thanks everybody, HH
 p.s.  shouldn't these last 2 H-C-H bond angles for CH4
 be 109.5 too???
        H2-C1-H5=109.5          H3-C1-H5=109.4424       H4-C1-H5=109.4424