# 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
```