Coordination-induced structure of theMg2pcore level ini−ZnMgRquasicrystals

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We present a detailed analysis of $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}2p$ photoemission (PE) spectra in icosahedral $\mathrm{Zn}\mathrm{Mg}R$ ($R=\mathrm{Y}$, Ho, Er) quasicrystals and in the crystalline ${\mathrm{Zn}}_{2}\mathrm{Mg}$ Laves phase. Synchrotron-radiation PE measurements were performed on in situ cleaved single-grain samples at ${10}^{\ensuremath{-}10}\phantom{\rule{0.3em}{0ex}}\mathrm{mbar}$ pressure and low, $90--150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, temperature. The analysis of $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}2p$ PE spectra in ${\mathrm{Zn}}_{2}\mathrm{Mg}$ reveals a surface shift of the core level of $\ensuremath{-}0.12\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}2p$ PE spectra in $i\text{\ensuremath{-}}\mathrm{Zn}\mathrm{Mg}R$ quasicrystals are essentially broadened as compared to spectra in ${\mathrm{Zn}}_{2}\mathrm{Mg}$ Laves phase. The effect is due to the coordination-induced structure of the $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}2p$ levels. Different local surroundings of Mg atoms in quasicrystals induce both different shifts of the $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}2p$ level and splittings of its spin-orbit components. The local coordination potential at different Mg sites in the quasicrystalline lattice is calculated on the basis of the face-centered icosahedral ZnMgY atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts calculated are spread within an interval of about $0.3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, while the splittings of the $2{p}_{3∕2}$ component are of the order of $1--10\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. The simulated theoretical $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}2p$ PE spectra of $\mathrm{fci}\text{\ensuremath{-}}\mathrm{Zn}\mathrm{Mg}R$ quasicrystals perfectly fit the experimental data.