Russo John, Wilding Nigel B
School of Mathematics, University of Bristol, Bristol BS8 1TW, United Kingdom.
Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom.
Phys Rev Lett. 2017 Sep 15;119(11):115702. doi: 10.1103/PhysRevLett.119.115702. Epub 2017 Sep 14.
Recent studies of melting in hard disks have confirmed the existence of a hexatic phase occurring in a narrow window of density which is separated from the isotropic liquid phase by a first-order transition, and from the solid phase by a continuous transition. However, little is known concerning the melting scenario in mixtures of hard disks. Here we employ tailored Monte Carlo simulations to elucidate the phase behavior of a system of large (l) and small (s) disks with diameter ratio σ_{l}/σ_{s}=1.4. We find that as small disks are introduced to a system of large ones, the stability window of the hexatic phase shrinks progressively until the line of continuous transitions terminates at an end point beyond which melting becomes a first-order liquid-solid transition. This occurs at surprisingly low concentrations of the small disks, c≲1%, emphasizing the fragility of the hexatic phase. We speculate that the change to the melting scenario is a consequence of strong fractionation effects, the nature of which we elucidate.
近期对硬盘中熔化现象的研究证实，在一个狭窄的密度窗口内存在一种六次近晶相，它通过一级相变与各向同性液相分离，通过连续相变与固相分离。然而，关于硬盘混合物中的熔化情况，我们所知甚少。在此，我们采用定制的蒙特卡罗模拟来阐明直径比为σₗ/σₛ = 1.4的大（l）盘和小（s）盘系统的相行为。我们发现，当向大磁盘系统中引入小磁盘时，六次近晶相的稳定性窗口逐渐缩小，直到连续相变线在一个端点处终止，超过该端点，熔化变为一级液 - 固相变。这在小磁盘浓度低至令人惊讶的c≲1%时就会发生，凸显了六次近晶相的脆弱性。我们推测，熔化情况的变化是强分馏效应的结果，我们对其性质进行了阐明。
