Thewes Filipe C, Fernandes Heitor C M
Instituto de Física, Universidade Federal do Rio Grande do Sul, CP 15051 91501-970, Porto Alegre, RS, Brazil.
Phys Rev E. 2020 Jun;101(6-1):062138. doi: 10.1103/PhysRevE.101.062138.
We study lattice gas systems on the honeycomb lattice where particles exclude neighboring sites up to order k (k=1,...,5) from being occupied by another particle. Monte Carlo simulations were used to obtain phase diagrams and characterize phase transitions as the system orders at high packing fractions. For systems with first-neighbors exclusion (1NN), we confirm previous results suggesting a continuous transition in the two-dimensional Ising universality class. Exclusion up to second neighbors (2NN) lead the system to a two-step melting process where, first, a high-density columnar phase undergoes a first-order phase transition with nonstandard scaling to a solidlike phase with short-range ordered domains and, then, to fluidlike configurations with no sign of a second phase transition. 3NN exclusion, surprisingly, shows no phase transition to an ordered phase as density is increased, staying disordered even to packing fractions up to 0.98. The 4NN model undergoes a continuous phase transition with critical exponents close to the three-state Potts model. The 5NN system undergoes two first-order phase transitions, both with nonstandard scaling. We, also, propose a conjecture concerning the possibility of more than one phase transition for systems with exclusion regions further than 5NN based on geometrical aspects of symmetries.
我们研究了蜂窝晶格上的晶格气体系统，其中粒子排除相邻位置，直至第k阶（k = 1，...，5）不被另一个粒子占据。蒙特卡罗模拟用于获得相图，并在高填充率下系统有序时表征相变。对于具有最近邻排除（1NN）的系统，我们证实了先前的结果，表明在二维伊辛普适类中存在连续转变。直到次近邻（2NN）的排除导致系统经历两步熔化过程，首先，高密度柱状相经历一阶相变，具有非标准标度，转变为具有短程有序域的类固相，然后，转变为无第二相变迹象的类流体构型。令人惊讶的是，3NN排除在密度增加时没有显示出向有序相的相变，即使在填充率高达0.98时仍保持无序。4NN模型经历连续相变，其临界指数接近三态Potts模型。5NN系统经历两次一阶相变，两者都具有非标准标度。我们还基于对称性的几何方面，对具有超过5NN的排除区域的系统存在不止一个相变的可能性提出了一个猜想。
