Title: Ensemble Sampling vs. Time Sampling in Molecular Dynamics Simulations of Thermal Conductivity

Abstract

Here, we compare time averaging and ensemble averaging as two different methods for phase space sampling in molecular dynamics (MD) calculations of thermal conductivity. For the comparison, we calculate thermal conductivities of solid argon and silicon structures, using equilibrium MD. Moreover, we introduce two different schemes for the ensemble averaging approach and show that both can reduce the total simulation time as compared to time averaging. It is also found that velocity rescaling is an efficient mechanism for phase space exploration. Although our methodology is tested using classical MD, the approaches used for generating independent trajectories may find their greatest utility in computationally expensive simulations such as first principles MD. For such simulations, where each time step is costly, time averaging can require long simulation times because each time step must be evaluated sequentially and therefore phase space averaging is achieved through sequential operations. Conversely, with ensemble averaging, phase space sampling can be achieved through parallel operations, since each trajectory is independent. For this reason, particularly when using massively parallel architectures, ensemble averaging can result in much shorter simulation times (similar to 100-200X), but exhibits similar overall computational effort.

Authors:

Gordiz, Kiarash ^[1]; Singh, David J. ^[2]; Henry, Asegun ^[1]

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+ Show Author Affiliations

1. Georgia Inst. of Technology, Atlanta, GA (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Thu Jan 29 00:00:00 EST 2015

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Energy Frontier Research Centers (EFRC) (United States). Solid-State Solar-Thermal Energy Conversion Center (S3TEC)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1185896

Alternate Identifier(s):

OSTI ID: 1286997

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 117; Journal Issue: 04; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

74 ATOMIC AND MOLECULAR PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY