Influence of vibrational entropy on structural stability of Nb-Si and Mo-Si systems at elevated temperatures

被引：57

作者：

Chen, Yue ^{[1
,2
]}

Hammerschmidt, T. ^{[2
]}

Pettifor, D. G. ^{[2
]}

Shang, Jia-Xiang ^{[1
]}

Zhang, Yue ^{[1
]}

机构：

[1] Beijing Univ Aeronaut & Astronaut, Sch Mat Sci & Engn, Beijing 100083, Peoples R China

[2] Univ Oxford, Dept Mat, Oxford OX1 3PH, England

来源：

ACTA MATERIALIA | 2009年 / 57卷 / 09期

基金：

英国工程与自然科学研究理事会;

关键词：

Transition metal silicides; Ab initio electron theory; Phase transformations; Elastic behavior; TRANSITION-METAL SILICIDES; ELASTIC-CONSTANTS; THERMAL-EXPANSION; SINGLE-CRYSTALS; ELECTRON-GAS; ENERGY; MO5SI3; PHASE;

D O I：

10.1016/j.actamat.2009.02.014

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

The heats of formation of stable and metastable phases of the Nb-Si and Mo-Si systems were studied using density functional theory (DFT). The high-temperature behavior of the competing phases was Studied by performing additional phonon calculations. Our theoretical results rationalize the major differences observed in the behavior of the Nb-Si and Mo-Si systems: Nb3Si is only stable at temperatures above 2043 K, whereas Mo3Si is always stable; Nb5Si3 and MoSi2, undergo phase changes at elevated temperatures, in contrast to Mo5Si3 and NbSi2. These differences are qualitatively explained by including the vibrational entropy to the free energies within the harmonic approximation. In particular, the softer shear moduli of the Nb5Si3 and MoSi2, beta phases cause their stabilities over the alpha phases at elevated temperature. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

引用

页码：2657 / 2664

页数：8

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