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Fabrication and Characterization of High-Q Silicon Nitride Membrane Resonators
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How to remove the spurious resonances from ring polymer molecular dynamics.
Mariana Rossi1, Michele Ceriotti2, David E Manolopoulos1
1Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
The Journal of Chemical Physics
|June 23, 2014
Summary
A new simulation method combines centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD) by adding a thermostat to internal ring polymer modes. This approach maintains RPMD
Area of Science:
- Quantum dynamics simulations
- Condensed phase systems
- Computational chemistry
Background:
- Centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD) are leading methods for simulating quantum dynamics.
- Practical differences lie in mass matrix choice and thermostat application to ring polymer internal modes.
Purpose of the Study:
- To explore a hybrid simulation method combining CMD and RPMD features.
- To investigate the impact of an internal mode thermostat on quantum dynamics approximations.
- To analyze the dependence of simulation accuracy on thermostat friction strength, particularly for vibrational spectroscopy.
Main Methods:
- Developed a method with physical particle masses and a Langevin thermostat on ring polymer internal modes.
- Analytically proved the validity of the internal mode thermostat for RPMD.
- Numerically explored the effect of varying Langevin friction on quantum dynamics approximations.
Main Results:
- The thermostatted RPMD method retains established RPMD properties and remains valid.
- The method is optimal in the short-time limit due to physical bead masses.
- Results are robust across a range of friction strengths, avoiding RPMD's resonance and CMD's curvature problems.
- Vibrational spectroscopy shows improved accuracy with this hybrid approach.
Conclusions:
- A continuous family of simulation methods exists, parameterized by Langevin friction.
- The proposed hybrid method offers a robust alternative for quantum dynamics simulations, particularly for vibrational spectroscopy.
- This approach mitigates known issues in CMD and RPMD, enhancing simulation reliability.
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