We will not go into great detail here of the input format of the MOLECULE input
file, as it is treated thoroughly in a separate chapter,
Chapter 
. Here we only present two inputs for
water ; one
using Cartesian coordinate input and
automatic symmetry detection and
the other using Cartesian coordinates and where we explicitly give the
symmetry elements. Finally we show the MOLECULE input for H 
O 
using Z-matrix input . In
all cases the basis set library of DALTON have been used, as we
assume that most users will exploit the basis sets provided in the basis
set library as opposed to punching them in. The punching
format for basis sets are described in detail in Sec. .
Let us first start with an input for water using Cartesian coordinates, and the very popular 6-31G** basis set.
BASIS
6-31G**
Water
6-31G** basis
2
8. 1
O .0000000000 -.2249058930 .0000000000
1. 2
H 1.4523499293 .8996235720 .0000000000
H -1.4523499293 .8996235720 .0000000000
The number on the fifth line denotes the number of blocks of atoms, in this case two, oxygen and hydrogen. There are one oxygen with charge 8, and two hydrogens with charge 1. The symmetry of the system will be detected by the program during the input processing unless turned off as shown in the last of the input examples for the MOLECULE \ input files.
We may also add the symmetry elements of the symmetry group ourselves. We must then remove any symmetry-dependent centers . For the above input this will result in, if we use the yz- and xy-planes as symmetry elements:
ATOMBASIS
Water
augmented correlation-consistent basis set of Dunning and coworkers
2 2 X Y
8. 1 ano-1 5 4 3 1
O .0000000000 -.2249058930 .0000000000
1. 1 ano-1 4 3 2
H 1.4523499293 .8996235720 .0000000000
In the above calculation we used the ANO set of
Widmark and
coworkers [3, 4]. We
use the contraction
[5s4p3d1f/4s3p2d] for the oxygen and the hydrogens respectively. We
also note the keyword ATOMBASIS which allows
different basis
functions to be used on different atoms.
Let us now proceed to an input for H O where we use
Z-matrix input . The input will then look like:
BASIS
sadlej
Vann - geometrioptimering med pVDZ
Prosjekt: Raman
3 2 0
O 1 8.0
H 2 1 0.97 1.0
H 3 1 0.97 2 104.5 1.0
The numbers on the fourth row denote respectively the number of atoms in the molecule (3), the charge of the molecule (+2), and the zero tells that symmetry is not to be used in this calculation. Note that unlike Cartesian coordinate input, which by default is in atomic units, the Z-matrix input is always to be in Ångstrøms.