Grzelak Adam, Gawraczyński Jakub, Jaroń Tomasz, Somayazulu Maddury, Derzsi Mariana, Struzhkin Viktor, Grochala Wojciech
Faculty of Chemistry, University of Warsaw , ul. Pasteura 1, 02-093 Warsaw, Poland.
Center of New Technologies, University of Warsaw , ul. Banacha 2C, 02-097 Warsaw, Poland.
Inorg Chem. 2017 May 15;56(10):5804-5812. doi: 10.1021/acs.inorgchem.7b00405. Epub 2017 May 2.
The X-ray diffraction data collected up to ca. 56 GPa and the Raman spectra measured up to 74.8 GPa for AgO, or AgAgO, which is a prototypical mixed valence (disproportionated) oxide, indicate that two consecutive phase transitions occur: the first-order phase transition occurs between 16.1 GPa and 19.7 GPa, and a second-order phase transition occurs at ca. 40 GPa. All polymorphic forms host the square planar [AgO] units typical of low-spin Ag. The disproportionated Imma form persists at least up to 74.8 GPa, as indicated by Raman spectra. Theoretical hybrid density functional theory (DFT) calculations show that the first-order transition is phonon-driven. AgO stubbornly remains disproportionated up to at least 100 GPa-in striking contrast to its copper analogue-and the fundamental band gap of AgO is ∼0.3 eV at this pressure and is weakly pressure-dependent. Metallization of AgO is yet to be achieved.
对于典型的混合价（歧化）氧化物AgO（或AgAgO），收集到的高达约56 GPa的X射线衍射数据以及测量到的高达74.8 GPa的拉曼光谱表明发生了两个连续的相变：在16.1 GPa和19.7 GPa之间发生一级相变，在约40 GPa处发生二级相变。所有多晶型体都含有低自旋Ag特有的平面正方形[AgO]单元。如拉曼光谱所示，歧化的Imma形式至少持续到74.8 GPa。理论杂化密度泛函理论（DFT）计算表明，一级相变是由声子驱动的。与铜类似物形成鲜明对比的是，AgO在至少100 GPa之前顽固地保持歧化状态，在此压力下，AgO的基本带隙约为0.3 eV，且与压力的相关性较弱。尚未实现AgO的金属化。
