Molecular modeling of metal hydrides: 2. Calculation of lattice defect structures and energies utilizing the Embedded Atom Method Page: 3 of 23
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WSRC-TR-90-275
Molecular Modeling of Metal Hydrides:
IL Calculation of Lattice Defect Structures and Energies Utilizing the Embedded
Atom Method
By
R. J. Wolf and K. A. Mansour
Westinghouse Savannah River Company
Savannah River Laboratory
Nuclear Reactor Technology and Scientific Computations
Aiken, SC 29808
ABSTRACT
Lattice defect structures and energies for palladium, nickel and aluminum computed include: single
vacancy, self-interstitial, intrinsic stacking fault, coherent twin boundary and (100), (110), and
(111) free surfaces. The importance of considering lattice defects in obtaining an accurate
Embedded Atom Method (EAM) description of real materials, and the application of the EAM to the
computation of lattice defect structures for palladium, nickel and aluminum is discussed. The EAM
functions developed in this study reproduce defect properties well and are suitable for future
investigations of metal hydrides involving defect related structures.
INTRODUCTION
This report is the second in a series of documents describing our progress in modeling properties of
metal hydrides. Reference to the initial report [WSRC-TR-90-156 or ref. 1] will be made,
particularly to the methodology employed there. The present report focuses on two issues: The
importance of considering lattice defects in obtaining an accurate Embedded Atom Method (EAM)
description of real materials, and the application of such a description to the computation of lattice
defect structures for palladium, nickel and aluminum.
Metal hydrides are vital SRS materials and will be used extensively for hydrogen/tritium storage and
handling in the new Replacement Tritium Facility. Examples of such metals and metal alloys
include palladium (Pd) and lanthanum-nickel-aluminum (LaNi5-xAlx, x=0.15 to 0.85). Metal
hydrides absorb large quantities of hydrogen/tritium, and the hydrogen density in these materials
can be much larger than that of liquid hydrogen. However, material degradation due to the
ingrowth of helium, one of tritium's radioactive decay products, causes unrecoverable damage.
Helium, although inert, tends to remain in the hydrides used at SRS once it is born. A clearer
understanding of such a phenomenon is the goal of this work.
The main focus is to fundamentally understand hydrogen/tritium and helium behavior and their
interactions in metal hydrides, with the intention to design better and more efficient tritium handling
materials and facilities. As a by-product of this work, we will be able to apply our state-of-the-art
techniques to study other problems involving hydrogen/tritium and helium in SRS materials.
Examples include hydrogen and helium interactions in lithium-aluminum reactor targets, tritium
reservoirs, and stainless steel reactor tanks.1
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Wolf, R.J. & Mansour, K.A. Molecular modeling of metal hydrides: 2. Calculation of lattice defect structures and energies utilizing the Embedded Atom Method, report, December 1, 1990; Aiken, South Carolina. (https://digital.library.unt.edu/ark:/67531/metadc1205296/m1/3/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.