Chem3D Users Manual - CambridgeSoft

Record Order
When sorted by Dihedral Angle, the order of the
records in the Torsional Parameters table and the
4-Membered Ring Torsional Parameters table is as
follows:
1. Records are sorted by the second atom type
number in the Dihedral Type field. For
example, the record for dihedral type 1-1-1-1 is
listed before the record for dihedral
type 1-2-1-1.
2. For records where the second atom type
number is the same, the records are sorted by
the third atom type number in the Dihedral
Type field. For example, the record for
dihedral type 1-1-1-1 is listed before the record
for dihedral type 1-1-2-1.
3. For multiple records where the second and
third atom type numbers are the same, the
records are sorted by the first atom type
number in the Dihedral Type field. For
example, the record for dihedral type 5-1-3-1 is
listed before the record for dihedral type 6-1-3-
1.
4. For multiple records where the first, second
and third atom type numbers are the same, the
records are sorted by the fourth atom type
number in the Dihedral Type field. For
example, the record for dihedral type 5-1-3-1 is
listed before the record for dihedral
type 5-1-3-2.
Out-of-Plane Bending
The Out-of-Plane Bending table (Out-of-Plane
Bending Parameters.xml) contains parameters
which are used to ensure that atoms with trigonal
planar geometry remain planar in MM2
calculations.
There are four fields in records in the Out-of-Plane
Bending Parameters table: Bond Type, Force
Constant, Quality and Reference.
Bond Type
The first field is the Bond Type which is described
by the atom type numbers of the two bonded
atoms.
For example, Bond Type 2-3 is a bond between an
alkene carbon and a carbonyl carbon.
Force Constant
The Force Constant field, or the out-of-plane
bending constant, field contains a measure of the
amount of energy required to cause a trigonal planar
atom to bend out-of-plane, i.e., to become nonplanar.
The larger the value of Force Constant for a
particular atom, the more difficult it is to coerce
that atom to be non-planar.
Record Order
When sorted by Bond Type, the order of the
records in the Out-of-Plane Bending Parameters
table is as follows:
1. Records are sorted by the first atom type
number in the Bond Type field. For example,
the record for bond type 2-1 is before the
record for bond type 3-1.
2. For records where the first atom type number
is the same, the records are sorted by the
second atom type number in the Bond Type
field. For example, the record for bond type 2-
1 is before the record for bond type 2-2.
NOTE: Out-of-plane bending parameters are not
symmetrical. For example, the force constant for a 2-3 bond
refers to the plane about the type 2 atom. The force constant
for a 3-2 bond refers to the plane about the type 3 atom.
Appendices
ChemOffice 2005/Appendix Parameter Tables • 287
Out-of-Plane Bending