High-temperature behavior of monolayer graphyne and graphdiyne
High-temperature behavior of monolayer graphyne and graphdiyne
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单层石墨炔和石墨二炔的高温行为
DOI：
10.1016/j.carbon.2015.12.086
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发表时间：
2016
期刊：
影响因子：
10.9
通讯作者：
K.W. Zhang
中科院分区：
文献类型：
--
作者：
ShuangYing Ma;Meng Zhang;L.Z. Sun;K.W. Zhang
采用自适应分子间反应键级（AIREBO）势对单层石墨炔和石墨二炔（MGY和MGDY）的高温行为进行了分子动力学模拟。在熔化过程中，MGY和MGDY经历三个连续的相变：（i）对于MGY和MGDY，分别从2800至2500 K开始转变为初始无定形石墨烯相（AGP），其中出现断键和大空穴;（ii）通过结构调整过程转变为AGP，直到T达到3650 K。该AGP将保持相对稳定，直到T <5000 K;（iii）AGP然后将逐渐转变为接近流体状态，T> 5000 K。甚至在第一相变之前，MGY和MGDY分别在1700和1200 K开始出现一些缺陷，例如5、7、8和9元环。除了严重的热振动引起的缺陷外，MGY和MGDY的急剧收缩和伴随的拉伸是初始AGP形成的决定性因素。与Kosterlitz-Halperin-Nelson-Young理论对二维材料熔化的预测相反，我们没有观察到六角相，而是观察到AGP作为中间相。
Molecular dynamics simulations with the adaptive intermolecular reactive bond order (AIREBO) potential are performed to study the high-temperature (T) behavior of monolayer graphyne and graphdiyne (MGY and MGDY). During the melting process, MGY and MGDY undergo three continuous phase transitions:(i) transformation into the initial amorphous graphene phase (AGP) starting from 2800 to 2500 K for MGY and MGDY, respectively, where broken bonds and large holes appear;(ii) transformation into AGP through a structural adjustment process until T reaches 3650 K. This AGP will remain relatively stable until T≈ 5000 K;(iii) the AGP will then gradually transform into a nearly fluid state for T> 5000 K. Even prior to the first phase transition, some defects, such as 5, 7, 8 and 9-membered rings start appearing at 1700 and 1200 K for MGY and MGDY, respectively. In addition to the defects derived from severe thermal vibration, the sharp contraction and accompanying stretch of MGY and MGDY are decisive in the formation of the initial AGP. In contrast to the prediction of the Kosterlitz-Thouless-Halperin-Nelson-Young theory for the melting of two-dimensional materials, we don't observe a hexatic phase but rather an AGP as an intermediate phase.