First‐principles lattice dynamics calculations of the phase boundary between β‐Si3N4 and γ‐Si3N4 at elevated temperatures and pressures
First‐principles lattice dynamics calculations of the phase boundary between β‐Si3N4 and γ‐Si3N4 at elevated temperatures and pressures
复制标题
第一原则高温高压下βSi3N4 和γSi3N4 之间相界的晶格动力学计算
DOI：
10.1002/jcc.21038
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发表时间：
2008
影响因子：
3
通讯作者：
Peter Kroll
中科院分区：
文献类型：
--
作者：
Atsushi Togo;Peter Kroll
采用准谐近似下的第一性原理晶格动力学方法研究了高温高压下β-Si 3 N4和γ-Si 3 N4之间的相界.我们发现相边界的正斜率，因此，在较高的温度下，需要较高的压力来合成氮化硅的高压多晶型物。结果表明，尖晶石型γ相的热膨胀大于菲安山岩型β相的热膨胀。另一方面，压力对β-Si 3 N4体积的影响大于对γ-Si 3 N4体积的影响，这反映在γ-Si 3 N4高达约40 GPa的较高体积模量上。因此，这些相的不同温度行为的起源是植根于与β-Si 3 N4相比，γ-Si 3 N4中零点能的更大体积依赖性。© 2008 Wiley Periodicals，Inc. J Comput Chem 2008
The phase boundary between β‐Si3N4and γ‐Si3N4is investigated at high pressure and high temperature using first‐principles lattice dynamics calculations within the quasi‐harmonic approximation. We find a positive slope of the phase boundary, hence, at higher temperatures it requires higher pressures to synthesize the high‐pressure polymorph of silicon nitride. It turns out that the thermal expansion of the spinel‐type γ‐phase is larger than that of the phenacite‐type β‐phase. On the other side, pressure affects more the volume of β‐Si3N4than of γ‐Si3N4, reflected in the higher bulk modulus of γ‐Si3N4up to about 40 GPa. The origin of the different temperature behavior of these phases, consequently, is rooted in a larger volume dependence of the zero point energy in γ‐Si3N4in comparison to β‐Si3N4. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008