Monte Carlo Simulation Code to Perform Simulations in the combined Reaction and Gibbs Ensemble

This code can be used to perform Monte Carlo (MC) simulations in the combined Reaction and Gibbs Ensemble. In these simulations, only Lennard-Jones interactions are considered. The directory "Source" contains the source code of the software written in Python. This code can be compiled using gfortran or Intel fortran compilers. The directory "Run" contains three example simulations. The subdirectories 'run_N2O4', 'run_NO2', and 'run_react' can be used to simulate phase and chemical equilibrium of pure N2O4 (at T=260K), pure NO2 (at T=240K) and the reactive mixture of NO2 and N2O4 (at T=270K). In the input files, the keywords represent:Ncycle: total number of MC cyclesNinit: number of initialization cyclesLinit: A logical that determines if the simulations start from a randomly generated configuration (.true.) or a configuration from a previous simulation (.false.). If started with a configuration from a previous simulation, a file called 'Coordold' needs to be present in the same directory (you can use the file 'Coordnew' generated at the end of each simulation).Temp: TemperaturePdisp: probability of choosing displacement trial movePswap: probability of choosing swap trial movePvol: probability of choosing volume trial movePreact: probability of choosing reaction trial moveDeltax: Maximum displacementDeltav: Maximum volume changeLnpt: If the simulation is conducted in NPT ensemble (.true.) or NVT ensemble (.false.). If NPT ensemble is chosen, the software only simulates one simulation box in NPT ensemble.Press: Pressure for NPT ensemble simulationsBox(1) and Box(2): Box sizes for the simulation boxes 1 and 2.Ncomp: Number of componentsNumber of Molecs for Each Box: The lines after this line shows the number of molecules for each component in each box. If two simulation boxes are simulated, there must be two lines, each showing the number of molecules of each component.Epsilon Sigma ln[Q] for each component: Three lines after this one show epsilon, sigma, and the natural logarithm of isolated molecule partition function for each component.Nreact: Number of reactions. Stoichiometry of each reactions should be given after this line.For more details, please refer to "Scaling Towards the Critical Point in the Combined Reaction/Gibbs Ensemble" from H. Mert Polat, Silvia Lasala, Frederick de Meyer, Celine Houriez, Othonas A. Moultos, and Thijs J. H. Vlugt.

本代码可用于开展联合反应与吉布斯系综（combined Reaction and Gibbs Ensemble）的蒙特卡洛（Monte Carlo, MC）模拟。此类模拟仅考虑伦纳德-琼斯（Lennard-Jones）相互作用。"Source"目录包含该软件的Python源代码，可通过gfortran或Intel Fortran编译器进行编译。"Run"目录包含三个示例模拟案例，其子目录‘run_N2O4’、‘run_NO2’与‘run_react’可分别用于模拟纯四氧化二氮（N₂O₄，T=260K）、纯二氧化氮（NO₂，T=240K）的相平衡与化学平衡，以及二氧化氮与四氧化二氮的反应混合物（T=270K）的相平衡与化学平衡。

输入文件中的关键字含义如下：
Ncycle：蒙特卡洛循环总次数
Ninit：初始化循环次数
Linit：逻辑变量，用于确定模拟初始配置：若设为.true.，则从随机生成的配置启动；若设为.false.，则从先前模拟得到的配置启动。若采用先前模拟的配置启动，则当前目录下需存在名为‘Coordold’的文件（可使用每次模拟结束时生成的‘Coordnew’文件）。
Temp：模拟温度
Pdisp：选择位移尝试移动的概率
Pswap：选择交换尝试移动的概率
Pvol：选择体积尝试移动的概率
Preact：选择反应尝试移动的概率
Deltax：最大位移量
Deltav：最大体积变化量
Lnpt：逻辑变量，用于指定模拟系综：若设为.true.，则采用NPT系综；若设为.false.，则采用NVT系综。若选择NPT系综，则软件仅在NPT系综下运行单个模拟盒。
Press：NPT系综模拟的目标压强
Box(1)与Box(2)：模拟盒1与模拟盒2的尺寸
Ncomp：组分数目
各模拟盒的分子数：该行之后的内容依次给出每个模拟盒中各组分的分子数目。若模拟两个盒子，则需提供两行内容，每行分别对应各组分的分子数。
各组分的ε、σ与ln[Q]：该行之后的三行内容依次给出每个组分的伦纳德-琼斯势阱深度（ε）、分子直径（σ）以及孤立分子配分函数的自然对数。
Nreact：反应数目。每个反应的化学计量比需紧随该行给出。

更多细节请参阅H. Mert Polat、Silvia Lasala、Frederick de Meyer、Celine Houriez、Othonas A. Moultos与Thijs J. H. Vlugt发表的论文《Scaling Towards the Critical Point in the Combined Reaction/Gibbs Ensemble》。