Constraint Algorithm Parameters

Constraint Mode

Parameter	Type	Default	Description
`constrain_mode`	string	none (constraints disabled)	Constraint algorithm

constrain_mode options:

Value	Description
`"SETTLE"`	SETTLE algorithm, specialized for rigid water molecules (triangle constraints)
`"SHAKE"`	SHAKE algorithm, general bond length constraints

The base constraint list is configured through the [constrain] prefix:

constrain_mode = "SHAKE"

[constrain]
mass = 3.3

Parameter	Type	Default	Description
`settle_disable`	bool	`false`	Top-level flag that disables SETTLE entirely

Parameter	Scope	Type	Default	Description
`iteration_numbers`	`SHAKE`	int	`25`	Maximum SHAKE iteration count
`step_length`	`SHAKE`	float	`1.0`	SHAKE step length / damping factor

Parameter	Scope	Type	Default	Description
`in_file`	`constrain`	string	-	Extra bond-constraint list file
`mass`	`constrain`	float	`3.3`, or `0.0` when `in_file` is set	Auto-constrain bonds involving atoms lighter than this threshold
`angle`	`constrain`	bool	`false`	Reserved, currently not implemented