Using the thermodynamic conditions describing the coexistence of two phases and the stability conditions of equilibrium state , we have calculated the normalized temperature and the normalized pressure of the triple point ( t1 , p1 ) , the melting curve , vapouring curve and the sublimation curve . the whole phase diagram of the 2d monatomic l - j system is obtained 和杜宜瑾等人的方法类似，我们先给出了系统在相变点时的一些参数的数值，在此基础上，考虑占据率q的因素，利用相平衡的热力学条件及平衡态的稳定性条件，得到了二维单元l - j系统的熔化曲线、汽化曲线、升华曲线以及三相点的位置，从而给出了该系统的完整的三相图。
