Brick-CFCMC: Open Source Software for Monte Carlo Simulations of Phase and Reaction Equilibria Using the Continuous Fractional Component Method

Abstract

We present a new molecular simulation code, Brick-CFCMC, for performing Monte Carlo simulations using state-ofthe-art simulation techniques. The Continuous Fractional Component (CFC) method is implemented for simulations in the NVT/ NPT ensembles, the Gibbs Ensemble, the Grand-Canonical Ensemble, and the Reaction Ensemble. Molecule transfers are facilitated by the use of fractional molecules which significantly improve the efficiency of the simulations. With the CFC method, one can obtain phase equilibria and properties such as chemical potentials and partial molar enthalpies/volumes directly from a single simulation. It is possible to combine trial moves from different ensembles. This enables simulations of phase equilibria in a system where also a chemical reaction takes place. We demonstrate the applicability of our software by investigating the esterification of methanol with acetic acid in a two-phase system.

Recent advances in the continuous fractional component Monte Carlo methodology

“…One of the promising applications of the CFCMC method is the possibility to combine phase-and reaction equilibria in high-density systems. Recently, Hens et al [62] performed simulations of esterification of ethanol with acetic acid (CH 3 OH + CH 3 COOH O CH 3 COOCH 3 + H 2 O) by combining the phase-and reaction equilibria using the CFCMC method. At equilibrium, this system consists of a water-rich phase and an ester-rich phase [62].…”

“…A detailed recipe to compute m 0 i from either the JANAF tables [174] or Gaussian09 [177] can be found in the supporting information of Ref. [62]. In Equation 8, the second term of the ideal gas part is related to the number density of species [28].…”

“…The benefits of using this method are most distinct when studying systems at high densities, e.g. chemisorption of CO 2 in monoethanol amine mixtures [64], absorption of CO 2 in reactive ionic liquid solutions [124], or esterification of ethanol with acetic acid [62]. Recently, Poursaeidesfahani et al [61] introduced an efficient alternative formulation of the CFCMC in the Reaction Ensemble (Rx/CFC).…”

“…By including Monte Carlo trial moves for sampling λ, different (expanded) ensembles such as the NPT-, grandcanonical-, reaction-, and Gibbs ensemble can be simulated. The CFCMC method has been used recently to study phase and reaction equilibria of several important systems [42,[61][62][63][64]. The expanded ensembles methodology and in particular CFCMC, compete with other methods such as Configurational-Bias Monte Carlo (CBMC) [65,66], Continuum Configurational Bias (CCB) [67][68][69], cavity biasing [70] and energy-biasing [71][72][73].…”

“…We have summarised our conclusions in Section 7. The algorithms presented in this manuscript have been incorporated in our open-source molecular simulation software, Brick-CFCMC [62]. The CFCMC algorithms are also implemented in the RASPA software [74,75].…”