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Molecular dynamics at constant Cauchy stress
Ronald E Miller1, Ellad B Tadmor2, Joshua S Gibson1
1Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Ontario K1S5B6, Canada.
The Journal of Chemical Physics
|May 16, 2016
Summary
The Parrinello-Rahman algorithm controls the second Piola-Kirchhoff stress, not the true Cauchy stress, in molecular dynamics. A modified algorithm directly controls Cauchy stress, improving simulation accuracy for materials under stress.
Area of Science:
- Computational materials science
- Condensed matter physics
- Molecular dynamics simulations
Background:
- The Parrinello-Rahman algorithm is a standard method for applying stress in molecular dynamics.
- This algorithm controls the second Piola-Kirchhoff stress, not the true Cauchy stress.
- Discrepancies between these stress measures can lead to misinterpretations in simulations.
Purpose of the Study:
- To address the limitations of the Parrinello-Rahman algorithm regarding stress control.
- To propose a modification for directly controlling the true Cauchy stress.
- To validate the improved algorithm's performance in simulating materials under stress.
Main Methods:
- Modification of the Parrinello-Rahman algorithm.
- Implementation of direct Cauchy stress control.
- Simulation of martensitic phase transformations under applied stress.
Main Results:
- The modified algorithm successfully controls the true Cauchy stress directly.
- Simulation results show the impact of direct Cauchy stress control on phase transformations.
- The proposed method offers a more accurate approach to stress application in molecular dynamics.
Conclusions:
- The direct control of Cauchy stress is crucial for accurate molecular dynamics simulations.
- The modified Parrinello-Rahman algorithm provides a more reliable method for imposing stress.
- This advancement is vital for studying material behavior under mechanical load, such as phase transformations.
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