期刊
PHYSICAL REVIEW B
卷 79, 期 21, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.79.214109
关键词
diffusion; dislocation structure; elastic constants; entropy; ferromagnetic materials; free energy; interstitials; iron; shear modulus; solid-state phase transformations; spin fluctuations
资金
- EPSRC [EP/G003955/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/G003955/1] Funding Source: researchfish
The stability of interstitial defect and dislocation structures in bcc Fe as a function of temperature is believed to play a crucial role in determining defect evolution under irradiation conditions. The vibrational properties of defects constitute one contribution to the corresponding energetics and much work has been done within the harmonic approximation to determine the vibrational formation free energy and formation entropy of such defects. Defects can however exhibit strong local strain fields that break the cubic symmetry of the bcc lattice leading to large anharmonicities and a breakdown of the harmonic approximation as an accurate means to calculate vibrational thermodynamic quantities. Moreover, if defect diffusion is active at a time scale comparable to an atomic vibration, strong anharmonicities will always be present at any finite temperature. The current work investigates the vibrational free energy and entropy of the << 110 >> self-interstitial dumbbell defect in bcc Fe using both harmonic and anharmonic free-energy calculation methods for a range of modern empirical potentials. It is found that depending on the empirical potential and for temperatures where diffusion is limited, the harmonic approximation is justified especially for empirical potentials that have been fitted to third-order elastic constants. The unique applicability range of such calculations for bcc Fe is also discussed given that with rising temperature spin fluctuations become increasingly important ultimately leading to a softening of the 110 shear modulus and to the alpha-bcc/gamma-bcc structural phase transformation.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据