Yu Liping, Raj Rishi
University of Colorado at Boulder Boulder, Colorado 80309, USA.
Sci Rep. 2015 Sep 30;5:14550. doi: 10.1038/srep14550.
A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown that the amorphous phase is thermodynamically stable. In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them. We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase. The approach highlights how density functional theory computations can be combined with the classical analysis of phase transformations to explain the behavior of a complex material. In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side.
本文提出了一种非晶态碳氧化硅（SiCO）热力学稳定性的模型。它基于一个被广泛认可的SiCO模型，该模型将SiCO设想为石墨烯的纳米域网络。这些域预计填充有SiO2分子，而与石墨烯的界面被认为包含混合键，即Si与C以及O原子键合。通常情况下，这些SiCO组合物预计会结晶。然而，量热测量表明非晶相在热力学上是稳定的。在本文中，我们采用第一性原理计算来估计石墨烯网络的界面能如何受到与其相连的混合键的有利影响。我们分析了界面能降低稳定非晶相的方式。该方法突出了密度泛函理论计算如何与相变的经典分析相结合来解释复杂材料的行为。此外，我们发现了一种二维晶格结构，其组成为Si2C4O3，由单层石墨烯构成，两侧分别与硅和氧键合。
