The MOLECULE -style input is originally based on the input for the MOLECULE \ integral program by Almlöf [74]. However, except for some lines still requiring formatted input, there are few remnants of the original input structure. The program supports both Cartesian and Z-matrix input of the molecular coordinates. However, the Z-matrix input provided is only a convenient way of describing the molecular geometry, as the Z-matrix is converted to Cartesian coordinates, which are then used in the subsequent calculations. Note that the Z-matrix input can only be used together with the basis set library.
The program includes an extensive basis set
library , and
additional possibilities for choosing the number of primitive
and contracted orbitals to be used with the Atomic Natural Orbital
(ANO) basis sets and the ``Not Quite van
Duijneveldt'' (NQvD) basis
sets . The large number of different basis sets
provided is in part
related to the variety of molecular properties with very different
basis set requirements that can be calculated with DALTON .
Most of the basis sets have been downloaded from the EMSL basis set
library service
(http://www.emsl.pnl.gov:2080/forms/basisform.html) [75].
Only six of the basis sets were obtained from different sources:
We note that each file containing a given basis sets contains the proper reference to be used when doing a calculation with a given basis set. We will give proper references for all basis sets in a subsequent chapter describing the input for the basis set library.
The description of the MOLECULE input is divided into four parts.
Section 
describes the general section of the
molecule input,
section describes the Cartesian coordinate
input ,
section describes the Z-matrix input , and finally
Section describes the basis set library .