Dimer-mediated cation diffusion in the stoichiometric ionic conductor Li 3 N
Dimer-mediated cation diffusion in the stoichiometric ionic conductor Li 3 N
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化学计量离子导体Li 3 N中二聚体介导的阳离子扩散
DOI：
10.1039/c5cp07625k
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发表时间：
2016
影响因子：
3.3
通讯作者：
Mulliner A
中科院分区：
文献类型：
--
作者：
Mulliner A
用非平衡分子动力学模拟了化学计量比Li3N在50<；T/K<；800温度范围内的阳离子扩散。所得扩散系数与已有的实验数据吻合较好。我们给出了扩散过程的详细原子描述。与以前研究得出的结论相反，我们的计算表明，没有必要利用少量本征缺陷的存在来启动扩散。该结构可以被认为是由组成Li2N和Li的交替层组成。随着温度的升高，越来越多的阳离子离开Li2N层，迁移到层间空间或Li层。那些进入层间空间的分子与Li2N层中的阳离子形成Li2二聚体，而那些进入邻近层的分子与其中的阳离子形成二聚体。两种类型的二聚体分别平行和垂直于[001]排列，寿命为∼3ps。由此产生的空位促进了Li2N层中的快速扩散，而层间阳离子运动导致了垂直于层的较慢的扩散。
Non-equilibrium molecular dynamics has been used to model cation diffusion in stoichiometric Li3N over the temperature range 50 < T/K < 800. The resulting diffusion coefficients are in excellent agreement with the available experimental data. We present a detailed atomistic account of the diffusion process. Contrary to the conclusions drawn from previous studies, our calculations show that it is unnecessary to invoke the presence of a small concentration of intrinsic defects in order to initiate diffusion. The structure can be considered to consist of alternating layers of composition Li2N and Li. As the temperature increases an increasing number of cations leave the Li2N layers and migrate either to the interlayer space or to the Li layer. Those that move into the interlayer space form Li2 dimers with cations in the Li2N layers and those that move into the neighboring layer form dimers with cations therein. The two types of dimer are aligned parallel and perpendicular to [001], respectively and have lifetimes of ∼3 ps. The vacancies so created facilitate rapid diffusion in the Li2N layers and the interlayer cation motion results in slower diffusion perpendicular to the layers.