Finite-Temperature Behavior of PdHx Elastic Constants Computed by Direct Molecular Dynamics. (30th May 2017)

• Record Type: Journal Article
• Authors: Zhou, X. W.; Heo, T. W.; Wood, B. C.; Stavila, V.; Kang, S.; Allendorf, M. D.
• Is Part Of: MRS advances. Volume 2:Number 55(2017)
• Page Start: 3341
• Page End: 3346
• Publication Date: 2017-05-30
• Subjects: Pd, -- hydrogenation, -- elastic properties; Electrical engineering -- Congresses; Physics -- Congresses; Materials -- Research -- Congresses; Materials science -- Congresses; 620.11
• DOI: 10.1557/adv.2017.387
• Languages: English
• ISSNs: 2059-8521

Abstract

ABSTRACT: 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. Literature mechanical testing experiments seem to support this hypothesis.