Force Field Properties
Force Field properties are used to specify the functional form of the force field, including bonded terms, van der Waals and electrostatics.
| Property | Type | Default | Description |
|---|---|---|---|
| bondterm | boolean | true | Specifies use of the bonding term for the AMOEBA potentials. |
| angleterm | boolean | true | Specifies use of the angle bending term for the AMOEBA potentials. |
| mpoleterm | boolean | true | Controls use of the permanent multipole electrostatics term for
the AMOEBA potential. Setting
mpoleterm to false also turns
off polarization, overriding the polarizeterm property below.
|
| opbendterm | boolean | true | Specifies use of the out-of-plane bending term for atoms at trigonal centers under the AMOEBA potentials. |
| pitorsterm | boolean | true | Specifies use of the pi-torsion term between atoms that have double bond character under the AMOEBA potentials. |
| polarizeterm | boolean | true | Controls use of polarizable electrostatics for the AMOEBA
potential. Setting
polarizeterm to false overrides the polarization
property below.
|
| polarization | string | mutual | [mutual/direct/none]
Mutual indicates the induced dipoles on each
atom interact self-consistently.
Direct indicates that induced dipoles
are influenced by the permanent multipoles, but not each other.
None turns off polarization.
|
| polar-eps | double | 1.0e-6 | This is the convergence criteria for the self-consistent field
calculation in units of RMS Debye. The default of 1e-6 is
necessary for optimizations to a tight tolerance. For optimization
during X-rey refinement to an RMS gradient per atom of 0.1, then
a looser
polar-eps of 1e-3 is sufficient. For molecular dynamics
with a thermostat, 1e-2 is resonable trade-off between accuracy
and performance.
|
| polar-sor | double | 0.70 | Calculation of the self-consistent field is based on successive
over-relaxtion (SOR). The
polar-sor parameter controls the fractional
change in the induced dipoles that is accepted prior to the beginning
of the following iteration. The default value of 0.70 does not usually
need to be changed, although in rare cases a slightly more conservative
value of 0.65 is necessary.
|
| strbndterm | boolean | true | Specifies use of the stretch-bend bond-angle coupling term for the AMOEBA potentials. |
| torsionterm | boolean | true | Specifies use of Fourier series torsional terms for AMOEBA potentials. |
| tortorterm | boolean | true | Specifies use of spline based torsion-torsion terms for AMOEBA protein and nucleic acid force fields. |
| ureyterm | boolean | true | Specifies use of the Urey-Bradley restraint between water hydrogen atoms for the AMOEBA water model. |
| vdwterm | boolean | true | Specifies use of the Buffered-14-7 van der Waals potential for the
AMOEBA force field. If set to
false, all non-bonded terms
are turned off.
|