非谐性
声子
凝聚态物理
热膨胀
非弹性中子散射
各向异性
声子散射
负热膨胀
材料科学
热容
非弹性散射
散射
物理
热力学
量子力学
作者
Dipanshu Bansal,Jiawang Hong,Chen W. Li,Andrew F. May,Wallace D. Porter,Michael Y. Hu,D. L. Abernathy,Olivier Delaire
出处
期刊:Physical review
日期:2016-08-09
卷期号:94 (5)
被引量:94
标识
DOI:10.1103/physrevb.94.054307
摘要
The anharmonic phonon properties of SnSe in the $Pnma$ phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.
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