Phonostat: thermostatting phonons in molecular dynamics simulations

Area of Science:

• Computational Physics
• Materials Science
• Chemical Physics

Background:

• Thermostat algorithms in molecular dynamics typically regulate system temperature by adjusting atomic velocities.
• Existing methods do not directly control energy within specific internal degrees of freedom.

Purpose of the Study:

• To present a new "phonostat" algorithm for regulating total energy in a specific internal degree of freedom during molecular dynamics simulations.
• To demonstrate the phonostat's ability to control energy exchange with a system.

Main Methods:

• The phonostat algorithm computes modal energies using a mode-tracking scheme at each time step.
• An external driving force of desired frequency and amplitude is applied to the system.
• Energy exchange is controlled via two distinct damping parameters and two schemes for driving force amplitude.

Main Results:

• The phonostat algorithm was successfully tested on a simple anharmonic oscillator, allowing for detailed parameter analysis.
• Application to a (10,0) carbon nanotube demonstrated the regulation of energy in highly anharmonic modes.

Conclusions:

• The phonostat algorithm offers a novel approach to precisely control energy within specific internal degrees of freedom in molecular dynamics.
• This method has potential applications in simulating systems with complex energy dynamics, such as anharmonic modes in nanomaterials.