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Title: Finite-Temperature Behavior of PdH x Elastic Constants Computed by Direct Molecular Dynamics

Abstract

In this paper, robust time-averaged molecular dynamics has been developed to calculate finite-temperature elastic constants of a single crystal. We find that when the averaging time exceeds a certain threshold, the statistical errors in the calculated elastic constants become very small. We applied this method to compare the elastic constants of Pd and PdH 0.6 at representative low (10 K) and high (500 K) temperatures. The values predicted for Pd match reasonably well with ultrasonic experimental data at both temperatures. In contrast, the predicted elastic constants for PdH 0.6 only match well with ultrasonic data at 10 K; whereas, at 500 K, the predicted values are significantly lower. We hypothesize that at 500 K, the facile hydrogen diffusion in PdH 0.6 alters the speed of sound, resulting in significantly reduced values of predicted elastic constants as compared to the ultrasonic experimental data. Finally, literature mechanical testing experiments seem to support this hypothesis.

Authors:
 [1];  [2];  [2];  [1];  [2];  [1]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
OSTI Identifier:
1429776
Alternate Identifier(s):
OSTI ID: 1463015
Report Number(s):
SAND2017-4865J; LLNL-JRNL-730861
Journal ID: ISSN 2059-8521; 653127
Grant/Contract Number:  
NA0003525; AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
MRS Advances
Additional Journal Information:
Journal Volume: 2; Journal Issue: 55; Journal ID: ISSN 2059-8521
Publisher:
Materials Research Society (MRS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Pd; hydrogenation; elastic properties

Citation Formats

Zhou, X. W., Heo, T. W., Wood, B. C., Stavila, V., Kang, S., and Allendorf, M. D. Finite-Temperature Behavior of PdHx Elastic Constants Computed by Direct Molecular Dynamics. United States: N. p., 2017. Web. doi:10.1557/adv.2017.387.
Zhou, X. W., Heo, T. W., Wood, B. C., Stavila, V., Kang, S., & Allendorf, M. D. Finite-Temperature Behavior of PdHx Elastic Constants Computed by Direct Molecular Dynamics. United States. doi:10.1557/adv.2017.387.
Zhou, X. W., Heo, T. W., Wood, B. C., Stavila, V., Kang, S., and Allendorf, M. D. Tue . "Finite-Temperature Behavior of PdHx Elastic Constants Computed by Direct Molecular Dynamics". United States. doi:10.1557/adv.2017.387. https://www.osti.gov/servlets/purl/1429776.
@article{osti_1429776,
title = {Finite-Temperature Behavior of PdHx Elastic Constants Computed by Direct Molecular Dynamics},
author = {Zhou, X. W. and Heo, T. W. and Wood, B. C. and Stavila, V. and Kang, S. and Allendorf, M. D.},
abstractNote = {In this paper, robust time-averaged molecular dynamics has been developed to calculate finite-temperature elastic constants of a single crystal. We find that when the averaging time exceeds a certain threshold, the statistical errors in the calculated elastic constants become very small. We applied this method to compare the elastic constants of Pd and PdH0.6 at representative low (10 K) and high (500 K) temperatures. The values predicted for Pd match reasonably well with ultrasonic experimental data at both temperatures. In contrast, the predicted elastic constants for PdH0.6 only match well with ultrasonic data at 10 K; whereas, at 500 K, the predicted values are significantly lower. We hypothesize that at 500 K, the facile hydrogen diffusion in PdH0.6 alters the speed of sound, resulting in significantly reduced values of predicted elastic constants as compared to the ultrasonic experimental data. Finally, literature mechanical testing experiments seem to support this hypothesis.},
doi = {10.1557/adv.2017.387},
journal = {MRS Advances},
number = 55,
volume = 2,
place = {United States},
year = {2017},
month = {5}
}

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