钴对PbTiO $_3$的加成诱导的双过氧化物酶结构：来自DFT和实验固态NMR光谱的见解
Double Perovskite Structure Induced by Co Addition to PbTiO$_3$ : Insights from DFT and Experimental Solid State NMR Spectroscopy
摘要：
从理论和实验两方面探讨了Co的加入对PbTiO $_3$化学结构和电子结构的影响。在溶胶-凝胶过程中将钴掺入到PbTiO $_3$中。化合物的XRD数据证实了纯样品的钙钛矿结构。随着Co掺入量的增加，XRD谱线变宽并显示出新兴的类金刚石特征。XRD图谱的变化被解释为双钙钛矿结构的形成。$^{207}$铅NMR测量显示了一个不断增长的各向同性组件中存在的Co。在与实验一致，DFT计算的化学位移值证实各向同性协调的Pb表明形成立方Pb $_2$ CoTiO $_6$域中制备的样品。最先进的杂化泛函第一性原理计算表明形成了具有立方结构的Pb $_2$ CoTiO $_6$，并证实了Co的加入可以显着降低氧结合能。实验紫外-可见光谱结果表明，在添加Co时，带隙向可见波长移动，这是由能带和吸收光谱计算证实的。通过程序升温还原（TPR）测量确定氧结合能。当添加Co时，TPR线向较低的温度移动，并且TPR图案中出现了新的特征。这种变化被解释为氧钴键强度减弱。通过DFT计算确定了Co插入后氧空位形成能和键长的改变所引起的电子结构的变化。
英文摘要：
The effects of Co addition on the chemical and electronic structure of PbTiO$_3$ were explored both by theory and through experiment. Cobalt was incorporated to PbTiO$_3$ during sol gel process. The XRD data of the compounds confirmed the perovskite structure for the pure samples. The XRD lines broadened and showed emerging cubic-like features as the Co incorporation increased. The changes in the XRD pattern were interpreted as double perovskite structure formation. $^{207}$Pb NMR measurements revealed a growing isotropic component in the presence of Co. In line with the experiments, DFT calculated chemical-shift values corroborate isotropic coordination of Pb suggesting the formation of cubic Pb$_2$CoTiO$_6$ domains in the prepared samples. The state-of-the-art hybrid functional first-principles calculations indicate formation of Pb$_2$CoTiO$_6$ with cubic structure and confirms that Co addition can decrease oxygen binding energy significantly. Experimental UV-Vis spectroscopy results indicate that upon addition of Co, the band gap is shifted towards visible wavelengths which was confirmed by the energy bands and absorption spectra calculations. The oxygen binding energies were determined by temperature programmed reduction (TPR) measurements. Upon addition of Co, TPR lines shifted to lower temperatures and new features appeared in the TPR patterns. This shift was interpreted as weakening of oxygen cobalt bond strength. The change in the electronic structure by the alterations of oxygen vacancy formation energy and bond lengths upon Co insertion are determined by DFT calculations.
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