Melting in two-dimensional systems has remained controversial as theory,simulations, and experiments show contrasting results. One issue that obscuresthis discussion is whether or not theoretical predictions on strictly 2Dsystems describe those of quasi-2D experimental systems, where out-of-planefluctuations may alter the melting mechanism. Using event-driven MolecularDynamics simulations, we find that the peculiar two-stage melting scenario of acontinuous solid-hexatic and a first-order hexatic-liquid transition asobserved for a truly 2D system of hard disks [Bernard and Krauth, Phys. Rev.Lett. 107, 155704 (2011)] persists for a quasi-2D system of hard spheres without-of-plane particle motions as high as half the particle diameter. Bycalculating the renormalized Young's modulus, we show that the solid-hexatictransition is of the Kosterlitz-Thouless type, and occurs via dissociation ofbound dislocation pairs. In addition, we find a first-order hexatic-liquidtransition that seems to be driven by a spontaneous proliferation of grainboundaries.
展开▼
机译：由于理论，模拟和实验显示出相反的结果，二维系统中的熔融仍存在争议。使讨论变得模糊的一个问题是，关于严格2D系统的理论预测是否描述了准2D实验系统的理论预测，其中平面外波动可能会改变熔化机制。使用事件驱动的MolecularDynamics模拟，我们发现，对于真正的2D硬盘系统，可以观察到连续的固-六相和一阶六-相-液相转变的特殊两阶段熔化情况[Bernard and Krauth，Phys。雷特牧师107，155704（2011）]提出了一种硬球的准2D系统，其平面内的粒子运动不超过粒子直径的一半。通过计算重新归一化的杨氏模量，我们表明固体-六价转变是Kosterlitz-Thouless类型的，并且通过结合位错对的解离而发生。此外，我们发现一阶六方液体转变似乎是由晶界的自发扩散驱动的。
展开▼
