Effect of shock on transition metal carbides and nitrides {MC/N (M = Zr, Nb, Ta, Ti)}
Effect of shock on transition metal carbides and nitrides {MC/N (M = Zr, Nb, Ta, Ti)}
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DOI：
10.1016/j.commatsci.2016.10.010
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发表时间：
2017-02
影响因子：
3.3
通讯作者：
C. Bhattacharya
中科院分区：
文献类型：
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作者：
C. Bhattacharya
我们在 Debye-Gruneisen 理论中研究了冲击冲击对一些过渡金属碳化物和氮化物 {MC/N (M= Zr, Nb, Ta, Ti)} 的影响。通过将 DFT 获得的总自由能与体积数据拟合到 Li 提出的状态方程 (EOS)，根据第一原理获得模型所需的参数。 EOS 模型用于预测这些化合物的冲击 Hugoniot 曲线，以验证压力和温度增加对 EOS 的影响。考虑到金属存在于 B 1 (NaCl) 相中，NbC、ZrC、TaC 和 ZrN 和 TiN 在高达～ 200 GPa 时与实验数据相当吻合。然而，对于 ZrC、TaC 和 ZrN，在较高压力（约 400 GPa）下可获得单个 Hugoniot 数据点。在所有三种情况下，对应于 B 1 相的预测 Hugoniot 与该压力下的实验数据点不匹配。这归因于金属中发生的结构相变。我们发现所有化合物在岩盐结构 (B1) 中都是稳定的，并在高压（超过 200 GPa）和 0 K 下转变为 CsCl (B2) 结构。由于实验是在有限温度下进行的，因此我们在有限温度下研究了这种转变。根据我们的分析，我们得出结论，在冲击载荷下的高压下不会发生 B 1 → B 2 转变。据我们所知，还没有关于这些化合物的转变的实验证据的报道。结构相变的唯一其他可能性是固液转变，即熔化。我们发现所有化合物在超过 200 GPa 的高压冲击载荷下都会熔化。
We investigated the effect of shock impact on some transition metal carbides and nitrides {MC/N (M= Zr, Nb, Ta, Ti)} within the Debye-Gruneisen theory. Parameters required for the model were obtained from first principles by fitting the total free energy vs. volume data obtained from DFT to the equation of state (EOS) proposed by Li. The EOS model was used to predict shock Hugoniot curves for these compounds to verify the effect of increasing pressures and temperatures on the EOS. Reasonably good agreement with experimental data was noted for NbC, ZrC, TaC and ZrN and TiN up to∼ 200 GPa considering the metals to exist in B 1 (NaCl) phase. However, in case of ZrC, TaC and ZrN, single Hugoniot data points were available at higher pressures (∼ 400 GPa). In all three cases, the predicted Hugoniot corresponding to B 1 phase did not match with the experimental data point at that pressure. This was attributed to a structural phase transition occurring in the metals. We found all the compounds to be stable in the rock salt structure (B1) and transform to CsCl (B2) structure at high pressures (beyond∼ 200 GPa) and 0 K. Since experiments are performed at finite temperatures, we investigated this transition at finite temperatures. From our analysis, we concluded that B 1→ B 2 transition does not occur at high pressures under shock loading. Experimental evidence of the transition has also not been reported for these compounds as per our knowledge. The only other possibility of a structural phase transition was solid-liquid transition ie melting. We found that all the compounds melt under shock loading at high pressures beyond∼ 200 GPa.