Yang Li-Ming, Ganz Ariel B, Dornfeld Matthew, Ganz Eric
School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Division of Nutritional Sciences, Cornell University, 339 Savage Hall, Ithaca, NY 14853, USA.
Condens Matter. 2016 Dec;1(1). doi: 10.3390/condmat1010001. Epub 2016 Mar 2.
Recently, freestanding atomically thick Fe metal patches up to 10 atoms wide have been fabricated experimentally in tiny pores in graphene. This concept can be extended conceptually to extended freestanding monolayers. We have therefore performed molecular dynamics simulations to evaluate the early melting stages of platinum, silver, gold, and copper freestanding metal monolayers. Our calculations show that all four freestanding monolayers will form quasi-2D liquid layers with significant out-of-plane motion and diffusion in the plane. Remarkably, we observe a 4% reduction in the Pt most likely bond length as the system enters the liquid state at 2400 K (and a lower effective spring constant), compared to the system at 1200 and 1800 K. We attribute this to the reduced average number of bonds per atom in the Pt liquid state. We used the highly accurate and reliable Density Functional Theory (DFT-D) method that includes dispersion corrections. These liquid states are found at temperatures of 2400 K, 1050 K, 1600 K, and 1400 K for platinum, silver, gold, and copper respectively. The pair correlation function drops in the liquid state, while the bond orientation order parameter is reduced to a lesser degree. Movies of the simulations can be viewed online (see Supplementary Material).
最近，已通过实验在石墨烯的微孔中制备出宽度达10个原子的独立原子厚铁金属片。这一概念在概念上可以扩展到扩展的独立单层。因此，我们进行了分子动力学模拟，以评估铂、银、金和铜独立金属单层的早期熔化阶段。我们的计算表明，所有这四种独立单层都会形成具有显著平面外运动和平面内扩散的准二维液体层。值得注意的是，与处于1200 K和1800 K的系统相比，当系统在2400 K进入液态时（以及有效弹簧常数更低），我们观察到铂最可能的键长减少了4%。我们将此归因于铂液态中每个原子平均键数的减少。我们使用了包括色散校正的高精度且可靠的密度泛函理论（DFT-D）方法。分别在2400 K、1050 K、1600 K和1400 K的温度下发现了铂、银、金和铜的这些液态。液态下对关联函数下降，而键取向序参数降低程度较小。模拟的影片可在线观看（见补充材料）。
