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Finite-Temperature Behavior of PdHx Elastic Constants Computed by Direct Molecular Dynamics

Journal Article · · MRS Advances
DOI:https://doi.org/10.1557/adv.2017.387· OSTI ID:1429776
 [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)
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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.
Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
Grant/Contract Number:
AC52-07NA27344; NA0003525
OSTI ID:
1429776
Alternate ID(s):
OSTI ID: 1463015
Report Number(s):
LLNL-JRNL--730861; SAND2017--4865J; 653127
Journal Information:
MRS Advances, Journal Name: MRS Advances Journal Issue: 55 Vol. 2; ISSN 2059-8521
Publisher:
Materials Research Society (MRS)Copyright Statement
Country of Publication:
United States
Language:
English

References (7)

Relation between static and dynamic Young's moduli of rocks journal December 1988
An atomistically validated continuum model for strain relaxation and misfit dislocation formation journal June 2016
Composition dependence of the elastic constants of β-phase and (α+β)-phase PdHx journal February 2010
Elastic constants of palladium and β -phase palladium hydride between 4 and 300 K journal August 1979
Elastic constants of nickel: Variations with respect to temperature and pressure journal June 1989
Mechanical stability of Pd-H systems: A molecular-dynamics study journal October 1992
An embedded-atom method interatomic potential for Pd–H alloys journal March 2008

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Related Subjects

36 MATERIALS SCIENCE
Pd
elastic properties
hydrogenation