We are developing a virtual consortium to produce more robust versions of these and other QChem programs. QChem is an area where terminology is important and the virtual consortium will be developing a hyperglossary to support the effort. Volunteers or contributions are welcome, especially for trying to normalise terms across the different programs. Note also that Units are important here as a wide variety is used and many programs do not explicitly add units.
Energies can be in calories, joules or hartrees and distances in meters, angstroms or bohrs.
Markup can be very valuable here and application programs should be able to convert between units. This was a simple SCF convergence using Gaussian94. The occupied energy levels are also shown, the most obvious effects being the large difference in the energy for the different atoms. In this example, VAMP has been used to calculate the C13 chemical shifts for a medium- sized molecule. Note also the Eigenvalues which have been displayed as a graph, showing the gap between occupied and unoccupied orbitals.