Atomistic Modeling of the Negative Thermal Expansion in δ-Plutonium Based on the Two-State Description

Materials

Tongsik Lee¹  Michael I. Baskes¹  A. C. Lawson¹  Shao Ping Chen¹ 

[1] Los Alamos National Laboratory, Los Alamos, NM 87545, USA; E-Mails:

关键词: plutonium;    negative thermal expansion;    Invar;    Weiss model;    modified embedded atom method;    Monte Carlo method;   

DOI  :  10.3390/ma5061040

来源: mdpi

【 摘 要 】

The δ phase of plutonium with the fcc structure exhibits an unusual negative thermal expansion (NTE) over its narrow temperature range of stability, 593–736 K. An accurate description of the anomalous high-temperature volume effect of plutonium goes beyond the current capability of electronic-structure calculations. We propose an atomistic scheme to model the thermodynamic properties of δ-Pu based on the two-state model of Weiss for the Invar alloys, inspired by the simple free-energy analysis previously conducted by Lawson et al. The two-state mechanism is incorporated into the atomistic description of a many-body interacting system. Two modified embedded atom method potentials are employed to represent the binding energies of two competing electronic states in δ-Pu. We demonstrate how the NTE takes place in δ-Pu by means of Monte Carlo simulations implemented with the two-state mechanism.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.