When the system being studied is an ion, the charge, n, on the ion must be supplied by CHARGE=n. For cations n can be 1, 2, 3, etc.; for anions -1 or -2 or -3, etc. Examples of various charged systems are given in the Table below.
If CHARGE=n is not present, the charge required by the
Lewis structure will be used. In
general, it is safer to use CHARGE=n because if a change is
accidentally made to the net charge, the error will be detected and the run
stopped.
If CHARGE=n is present, including CHARGE=0, that charge will be used, unless
it is in conflict with the Lewis structure, in which case the job will be
stopped.
If both GEO-OK and CHARGE=n
are
present, that charge will be used, unless it is in conflict with the Lewis
structure, in which case the charge required by the Lewis structure will be
used. (This is not a useful option; it is equivalent to CHARGE=n
being absent)
In cases where the charge supplied is in conflict with that required by the Lewis structure, the Lewis structure will be printed. That, together with the printed charged sites, will allow the correct charge to be determined.
To change the charge calculated by MOZYME use one or more of the following keywords:
METAL - Change the formal
charge of a
metal atom.
SETPI - Change Lewis structure
by adding and deleting π-bonds.
CVB - Change the topography of the system
by making and deleting connectivities.
Table:
Use of CHARGE=n
Ion |
Keyword |
Ion |
Keyword |
|
|
|
|
NH4+ |
CHARGE=1 |
CH3COO- |
CHARGE=-1 |
C2H5+ |
CHARGE=1 |
(COO)= |
CHARGE=-2 |
SO4= |
CHARGE=-2 |
PO4-3 |
CHARGE=-3 |
HSO4- |
CHARGE=-1 |
H2PO4- |
CHARGE=-1 |