Subject: SOME SAMPLE ZMATRICES

From: "E. Lewars" <[email-masked]>
Date: Thu, 25 May 1995 10:53:20 -0400

1995 May 25

T. Koch asked for examples of Z-matrices which constrain molecules to some
particular symmetry, about a week ago.

Although Z-matrices may be on the way out (Warren J. Hehre *Practical
Strategies for Electronic Structure Calculations*, pp 20, 21), here are some
(the art of writing Z-mat's is discussed in *A Handbook of Computational
Chemistry* by Tim Clark, ca. 1984, and in *Exploring Chemistry with Electronic
Structure Methods* by J. B. Foresman and A. Frisch):
--------------------

# Fopt=(CalcHFFC) mp2 6-31G* scf=direct

MP2/6-31G* opt on CO2 cyclic dimer; input: HF/6-31G* geom (D2h)

  0 1
  X1
  X2     X1     1.
  X3     X2     X3X2     X1      90.
  X4     X2     X3X2     X1      90.     X3     180.
  C5     X1     X3X2     X2      90.     X3       0.
  O6     X1     O6X1     X2      90.     X3     -90.
  C7     X1     X3X2     X2      90.     X3     180.
  O8     X1     O6X1     X2      90.     X3      90.
  O9     C5     O9C5     X3      90.     X2     180.
  O10    C7     O9C5     X4      90.     X2     180.

  X3X2           0.9369
  O6X1           0.9880
  O9C5           1.1525

================================

# Fopt=(CalcHFFC) mp2 6-31G* scf=direct

MP2/6-31G* opt on H2CO3; input: HF/3-21G (sic, 3-21G) geom (C2v)

  0 1
  O1
  C2     O1     C2O1
  O3     C2     O3C2     O1      A321
  O4     C2     O3C2     O1      A321    O3     180.
  H5     O4     H5O4     C2      A542    O1       0.
  H6     O3     H5O4     C2      A542    O1       0.

  C2O1           1.202
  O3C2           1.332
  H5O4           0.966
  A321         125.4
  A542         111.8

=================================

# mp4 6-31+G* scf=direct

MP4/6-31+G* single-p on CO2; MP2/6-31G* geom (Dih)

  0 1
  O1
  C2     O1     C2O1
  X3     C2     1.       O1      90.
  O4     C2     C2O1     X3      90.     O1     180.

  C2O1           1.1797
==============================

# 3-21G Fopt scf=direct

   PROPANE. Doubly eclipsed conformation (C2v).  Input params from MM (Sybyl)

 0 1
C1
C2  C1  C2C1                                  NOTE THAT HERE, AND IN BUTANE,
C3  C2  C2C1   C1  A321                       BELOW, AFTER THE DIHEDRAL FOR
H4  C3  H4C3   C2  A432   C1    0.            THE 1ST H OF A CH3 IS DEFINED
H5  C3  H5C3   C2  A532   H4    D5324         (e.g. 0., FOR D4321) THE DIHED
H6  C3  H5C3   C2  A532   H4   -D5324         FOR THE OTHER OTHER TWO CH3 H'S
H7  C1  H4C3   C2  A432   C3    0.            IS REFERRED BACK TO THE 1ST H
H8  C1  H5C3   C2  A532   H7    D5324         (e.g. D5324, NOT D5321); THIS
H9  C1  H5C3   C2  A532   H7   -D5324         MAY SOMETIMES SPEED UP
H1O C2  H10C2  C1  A1021  C3    D10213        OPTIMIZATION BY ALLOWING A
H11 C2  H10C2  C1  A1021  C3   -D10213        CH3 TO BE ROTATED AS A UNIT

C2C1   1.562
H4C3   1.099
H5C3   1.102
H10C2  1.109
A321   115.0
A432   113.3
A532   110.6
A1021  108.8
D5324  120.6
D10213 122.3
=================

# am1 Scan Nosym

PES scan on butane. C2C1 (central CC) from 1.510-->1.520 in 21 steps of 0.001
D4123 from 0-->360 in 37 steps of 10.  All other params frozen.
38X22=836 points  [D4123 = 180. represents the staggered conf.]

 0 1
C1
C2  C1  C2C1
C3  C2  1.508  C1  113.
C4  C1  1.508  C2  113.  C3    D4123
H5  C3  1.117  C2  111.  C1    180.
H6  C3  1.117  C2  111.  H5    120.
H7  C3  1.117  C2  111.  H5   -120.
H8  C4  1.117  C1  111.  C2    180.
H9  C4  1.117  C1  111.  H8    120.
H1O C4  1.117  C1  111.  H8   -120.
H11 C2  1.123  C1  109.  C3    122.
H12 C2  1.123  C1  109.  H11   117.
H13 C1  1.123  C4  109.  H9    178.
H14 C1  1.123  C4  109.  H9     62.

C2C1   1.510   21   0.001
D4123  0.      37  10.
====================

# 6-31G*  scf=direct

2-PROPENOL. The Cs conformer with H-O/C=C eclipsed; C-H of Me/C=C eclipsed.
  Single-point job.

 0 1
C1
C2  C1  1.340
O3  C2  1.386  C1  120.5
H4  O3  0.967  C2  107.5  C1    0.
C5  C2  1.484  O3  114.2  C1    180.
H6  C5  1.118  C2  110.4  C1    0.
H7  C5  1.118  C2  110.3  H6   -120.5
H8  C5  1.118  C2  110.3  H6    120.5
H9  C1  1.095  C2  121.5  O3    180.
H1O C1  1.096  C2  122.3  O3      0.
=======================

WATER, C2v

0 1
H1
O2   H1   O2H1
H3   O2   O2H1   H1   A321

[then give O2H1 etc]
======================

WATER, C2v [here a dummy atom is used to position the molecule nice and
symmetrically in the coord. system; this may make it easier to interpret
the results]

0 1
O1
X2   O1   1.
H3   O1   H3O1   X2   A312
H4   O1   H3O1   X2   A312
=============================
===============================
Errol Lewars
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