Structural Transitions in Monolayer MoS2 by Lithium Adsorption
Structural Transitions in Monolayer MoS2 by Lithium Adsorption
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DOI：
10.1021/jp510083w
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发表时间：
2015-05-14
影响因子：
3.7
通讯作者：
Peeters, F. M.
中科院分区：
文献类型：
--
作者：
Esfahani, D. Nasr;Leenaerts, O.;Peeters, F. M.
基于第一性原理计算，我们研究了Li掺杂后单层MoS2的H相和T相的结构稳定性。我们的计算表明，通过在 MoS2 表面吸附 Li 原子，可以将 MoS2 扭曲的 T 相稳定在 H 相之上。通过分子动力学和声子计算，我们表明MoS2的T相是动态不稳定的并且发生相当大的畸变。畸变的类型取决于所吸附的锂原子的浓度，并且当增加锂掺杂时，畸变会从锯齿形变为菱形。将稳定的 H 相转变为扭曲的 T 相存在很大的能量势垒，通过增加 Li 原子的浓度可以大大降低该能量势垒。我们表明，Li 原子必须吸附在 MoS2 单层的两侧，以充分降低势垒。研究了允许这种双面吸附的两个过程，即穿过 MoS2 层的渗透和在 MoS2 表面上的扩散。我们表明，虽然表面扩散只有 0.24 eV 的小势垒，但穿过纯 MoS2 层所需的能量约为或等于 2 eV。然而，当MoS2层被Li原子覆盖时，Li原子穿透该层所需获得的能量大大减少，穿透变得可行。
Based on first-principles calculations, we study the structural stability of the H and T phases of monolayer MoS2 upon Li doping. Our calculations demonstrate that it is possible to stabilize a distorted T phase of MoS2 over the H phase through adsorption of Li atoms on the MoS2 surface. Through molecular dynamics and phonon calculations, we show that the T phase of MoS2 is dynamically unstable and undergoes considerable distortions. The type of distortion depends on the concentration of adsorbed Li atoms and changes from zigzag-like to diamond-like when increasing the Li doping. There exists a substantial energy barrier to transform the stable H phase to the distorted T phases, which is considerably reduced by increasing the concentration of Li atoms. We show that it is necessary that the Li atoms adsorb on both sides of the MoS2 monolayer to reduce the barrier sufficiently. Two processes are examined that allow for such two-sided adsorption, namely, penetration through the MoS2 layer and diffusion over the MoS2 surface. We show that while there is only a small barrier of 0.24 eV for surface diffusion, the amount of energy needed to pass through a pure MoS2 layer is of the order of similar or equal to 2 eV. However, when the MoS2 layer is covered with Li atoms the amount of energy that Li atoms should gain to penetrate the layer is drastically reduced and penetration becomes feasible.