Hydroxide-ion incorporation and conduction mechanisms in tin pyrophosphate – a firstprinciples study
Hydroxide-ion incorporation and conduction mechanisms in tin pyrophosphate – a firstprinciples study
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焦磷酸锡中氢氧根离子的结合和传导机制
DOI：
10.1039/c5ta01676b
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发表时间：
2015
影响因子：
11.9
通讯作者：
Katsuyuki Matsunaga
中科院分区：
文献类型：
--
作者：
Junya Terasaka;Kazuaki Toyoura;Atsutomo Nakamura;Katsuyuki Matsunaga
在第一性原理计算的基础上，从理论上研究了氢氧化物离子在焦磷酸锡（SnP2O7）中的掺入和传导机理。氢氧根离子不是简单地结合到晶体的间隙位置，并且结合伴随着P2O7单元（焦磷酸盐离子）解离成两个PO4单元。计算了各种天然缺陷的形成能，发现间隙的质子和氢氧根离子是主要的缺陷种类，它们的浓度可以通过掺杂杂价阳离子来控制。在第一性原理分子动力学模拟中观察到氢氧根离子的远程迁移，但在模拟过程中其频率极低。事实上，计算出的传导途径的势垒非常高（1.92 eV），并且SnP2O7的估计体电导率远低于实验报道的电导率。这些结果表明，实验观察到的SnP2O7的氢氧离子电导率不能简单地用氢氧离子在晶格中的运动来解释。
The incorporation and conduction mechanisms of hydroxide ions in tin pyrophosphate (SnP2O7) have been investigated theoretically on the basis of first-principles calculations. Hydroxide ions are not simply incorporated into interstitial sites in the crystal, and the incorporation is accompanied by dissociation of a P2O7 unit (pyrophosphate ion) into two PO4 units. From the calculated formation energies of various native defects, it was found that the interstitial proton and hydroxide ion are the dominant defect species and their concentrations can be controlled by doping heterovalent cations. The long-range migration of the hydroxide ion was observed in the first-principles molecular dynamics simulations, but its frequency during the simulation was extremely low. In fact, the calculated potential barrier for the conduction pathway was extremely high (1.92 eV), and the estimated bulk conductivity in SnP2O7 was much lower than the experimentally reported conductivities. These results indicate that the experimentally observed hydroxide-ion conductivity of SnP2O7 cannot be simply explained by motion of hydroxide ions through the crystal lattice.