利用Peng_Robinson EOS 计算常见纯组分气体逸度和密度。利用matlab运行求解。-Peng Robinson is used to calculate the density and fugacity of single component gas at given pressure with Peng-Robinson equation.

PR方程编写，密度根求解；逸度系数求解，混合规则改进(PR equation writing, density root solving; The fuzziness coefficient is solved and the mixing rule is improved)