mstk.forcefield.SDKAngleTerm

class mstk.forcefield.SDKAngleTerm(type1, type2, type3, theta, k)

Angle term in SDK function form

The energy function is

>>> U = k * (theta-theta0)^2 + LJ96
>>> LJ96 = 6.75 * epsilon * ((sigma/r)^9 - (sigma/r)^6) + epsilon, r < 1.144714 * sigma

The angle is in unit of radian, and the force constant is in unit of kJ/mol/rad^2.

This term itself does not contain parameters epsilon and sigma. Instead, it expects a MieTerm between type1 and type3 existing in the ForceField object. If such a MieTerm does not exist, or the repulsion and attraction of this MieTerm do not equal to 9 and 6, then the ForceField is invalid and cannot be used to construct a System.

During the initialization, the two side atom types will be sorted by their string.

Parameters:

• type1 (str) –

• type2 (str) –

• type3 (str) –

• theta (float) –

• k (float) –

type1

Type:

str

type2

Type:

str

type3

Type:

str

theta

Type:

float

k

Type:

float

fixed

Type:

bool

Methods

__init__(type1, type2, type3, theta, k)
evaluate_energy(val)	Evaluate the energy for a force field term like HarmonicBondTerm, PeriodicDihedralTerm, etc...
get_alias()	Return a short alias for the name of this class
to_zff()	Pack the attributes of a term into a string so that can be saved into a line in ZFF file.
to_zff_header()	Header string to explain a line in ZFF format
to_zfp()	Pack the attributes of a term into a dict so that can be saved into ZFP xml file.

Attributes

is_linear	Whether or not this angle term is linear.
name	The name of this force field term.

property is_linear

Whether or not this angle term is linear.

Returns:

is

Return type:

bool