TINKER is also able to perform rigid-body calculations and stochastic dynamics.
Rigid-body calculations
In order to perform rigid body calculations, the following keywords need to be added to the key file:
group-molecule
group-inter
integrator rigidbody
Here, each molecule in the system is set to be a group and only inter-group interactions are considered. Therefore, each molecule is treated as a rigid body. The INTEGRATOR keyword is use to set the proper integration method used to perform molecular dynamics.
A special version of minimize and optimize must be used when rigid bodies are defined: minrigid and optrigid
Stochastic dynamics
In order to perform a stochastic molecular dynamics, the following keyword need to be added to the key file:
integrate stochastic
The INTEGRATOR keyword is use to set the proper integration method used to perform molecular dynamics.
Also, the keyword FRICTION is used to specify the frictional coefficient in ps-1 for use with stochastic dynamics. The default value used in the absence of the FRICTION keyword is 91.0, which is generally appropriate for water.
**TINKER 4.x and 5.x both use INTEGRATE instead of INTEGRATOR. Documentation for Tinker 6.x has not been updated yet **
