高温高压下过渡金属Ru的结构相变*
Structural phase transition of Ru at high pressure and temperature
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摘要: 采用基于密度泛函理论的第一性原理和准简谐晶格动力学方法对Ru的六角密排(hcp)、面心立方(fcc)、体心四方(bct)和体心立方(bcc)结构的磁性、晶格结构稳定性和高温高压下的相变进行了系统的研究。计算获得了各相结构的磁性基态及其稳定性范围,结果表明:零温下在计算的压力范围内, NM-hcp结构是Ru最稳定的结构,压力的单独作用下并没有相变的发生;NM-fcc结构是Ru的亚稳定结构,而NM-bcc和FM-bct结构在动力学上并不稳定。高温高压下Ru将发生从NM-hcp到NM-fcc结构的相变,并给出了Ru的温度压力相图。Abstract: The magnetism, stabilities and phase transition of Ru in hcp, fcc, bct and bcc structures are investigated with detailed first-principles calculations based on density-functional theory and quasiharmonic lattice dynamics approximation. Magnetic ground states and stability ranges of various phases are obtained. Calculated results indicate that the non-magnetic (NM)-hcp structure is the most stable in the entire pressure range at zero temperature, and the structural transition cannot be induced by pressure alone. NM-fcc structure is a metastable phase of bulk Ru, while both the NM-bcc and ferromagnetic (FM)-bct structures are dynamically unstable. At high pressure and temperature, a transformation from NM-hcp to NM-fcc structure will occur. Finally, the pressure-temperature phase diagram of Ru is presented.
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