FiniteTemperature Behavior of PdH _{x} Elastic Constants Computed by Direct Molecular Dynamics
Abstract
In this paper, robust timeaveraged molecular dynamics has been developed to calculate finitetemperature 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:

 Sandia National Lab. (SNLCA), Livermore, CA (United States)
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Publication Date:
 Research Org.:
 Sandia National Lab. (SNLCA), 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 (EE3F)
 OSTI Identifier:
 1429776
 Alternate Identifier(s):
 OSTI ID: 1463015
 Report Number(s):
 SAND20174865J; LLNLJRNL730861
Journal ID: ISSN 20598521; 653127
 Grant/Contract Number:
 NA0003525; AC5207NA27344
 Resource Type:
 Accepted Manuscript
 Journal Name:
 MRS Advances
 Additional Journal Information:
 Journal Volume: 2; Journal Issue: 55; Journal ID: ISSN 20598521
 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. FiniteTemperature 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. FiniteTemperature 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 .
"FiniteTemperature 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 = {FiniteTemperature 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 timeaveraged molecular dynamics has been developed to calculate finitetemperature 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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