Yang Li-Ming, Frauenheim Thomas, Ganz Eric
Bremen Center for Computational Materials Science, University of Bremen, Am Falturm 1, 28359, Bremen, Germany.
Phys Chem Chem Phys. 2015 Aug 14;17(30):19695-9. doi: 10.1039/c5cp03465e. Epub 2015 Jul 13.
Although significant progress in the fabrication and applications of graphene-like materials has been made, free-standing metal monolayers are extremely rare due to the challenges in fabrication. Furthermore, such structures are often unstable versus 3D close-packed forms. Silver is an important noble metal with many unique properties, and has a wide range of applications in daily life and industry. Here, we display a new dimension of silver, i.e., a 2D Ag monolayer, with reduced dimensionality and quantum confinement. We observe that the Ag monolayer is stable in ab initio molecular dynamics simulations up to 800 K for 10 ps. The bond strength per atom actually increases from 0.21 eV for the bulk with twelve bonds to 0.33 eV for the 2D layer with six bonds. This increase in bond strength contributes to the stability of the free-standing 2D layer. Detailed density functional theory calculations are used to predict the properties of this material. The 2D Ag monolayer is the global minimum structure. One electron is delocalized into the whole sheet and is donated to a nearly free 2D electron gas.
尽管类石墨烯材料的制备和应用已取得显著进展，但由于制备方面的挑战，独立的金属单层极为罕见。此外，相对于三维密堆积形式，此类结构通常不稳定。银是一种具有许多独特性质的重要贵金属，在日常生活和工业中有广泛应用。在此，我们展示了银的一个新维度，即二维银单层，具有降低的维度和量子限制。我们观察到，在高达800K的从头算分子动力学模拟中，银单层在10皮秒内是稳定的。每个原子的键强度实际上从具有十二个键的体相的0.21电子伏特增加到具有六个键的二维层的0.33电子伏特。键强度的这种增加有助于独立二维层的稳定性。详细的密度泛函理论计算用于预测这种材料的性质。二维银单层是全局最小结构。一个电子离域到整个薄片中，并贡献给近乎自由的二维电子气。
