Development of a Flexible‐Monomer Two‐Body Carbon Dioxide Potential and Its Application to Clusters up to (CO₂)₁₃

Abstract

A flexible-monomer two-body potential energy function was developed that approaches the high level CCSD(T)/CBS potential energy surface (PES) of carbon dioxide (CO ) systems. This function was generated by fitting the electronic energies of unique CO monomers and dimers to permutationally invariant polynomials. More than 200,000 CO configurations were used to train the potential function. Comparisons of the PESs of six orientations of flexible CO dimers were evaluated to demonstrate the accuracy of the potential. Furthermore, the potential function was used to determine the minimum energy structures of CO clusters containing as many as 13 molecules. For isomers of (CO ) , the potential demonstrated energetic agreement with the M06-2X functional and structural agreement of the B2PLYP-D functional at substantially reduced computational costs. A separate function, fit to MP2/aug-cc-pVDZ reference energies, was developed to directly compare the two-body potential to the ab initio MP2 level of theory. © 2017 Wiley Periodicals, Inc.

Data-Driven Many-Body Models for Molecular Fluids: CO2/H2O Mixtures as a Case Study

“…In the simulations of CO 2 (H 2 O) 20 , the interactions between the water molecules were described by the many-body MB-pol PEF − that accurately reproduces the properties of water from the gas to the condensed phase. , In the calculations of ref , many-body effects are thus only considered between H 2 O molecules through the MB-pol PEF and are neglected between CO 2 and H 2 O molecules since these interactions are described by a strictly 2B PEF. More recently, a 2B PEF for CO 2 was developed from CCSD­(T)-F12b/aug-cc-pVTZ reference data and used in the analysis of both structures and energetics of small (CO 2 ) N clusters with N ≤ 13, which were found to be in good agreement with results obtained using density functional theory (DFT) with the M06-2X and B2PLYP-D functionals …”

“…[36][37][38]40 More recently, several models that include many-body effects, either implicitly or explicitly, have been proposed. 51,52,55,57,58 An analytical representation of the potential energy surface of the CO 2 dimer (with rigid CO bonds) was derived from reference energies obtained at the symmetry adapted perturbation theory (SAPT) level and used to calculate the second virial coefficient that was found to be in good agreement with the corresponding experimental data. 39 SAPT calculations were also used to develop an implicit many-body model of CO 2 with rigid CO bonds and polarization effects represented by the Drude model.…”

“…74,75 More recently, a 2B PEF for CO 2 was developed from CCSD(T)-F12b/aug-cc-pVTZ reference data and used in the analysis of both structures and energetics of small (CO 2 ) N clusters with N ≤ 13 which were found to be in good agreement with results obtained using density functional theory (DFT) with the M06-2X and B2PLYP-D functionals. 58 In this study, we present full-dimensional many-body PEFs for neat CO 2 and CO 2 /H 2 O mixtures developed within the TTM-nrg and MB-nrg theoretical/computational frameworks originally introduced to represent the interactions of halide 68,69 and alkali-metal ions 70,71 with water. Through a detailed analysis of the energetics of small clusters, many-body contributions, virial coefficients of gas mixtures, and structural properties of liquid mixtures, we demonstrate that the MB-nrg PEFs provide highly accurate representations of neat CO 2 and CO 2 /H 2 O mixtures from the gas to the condensed phase.…”

“…From a theoretical standpoint, electronic structure calculations and molecular dynamics (MD) simulations have been used to model the energetics, as well as the structural, thermodynamic, and dynamical properties of CO 2 , in both single- and multicomponent systems. − Most of the early molecular models adopted relatively simple functional forms parametrized to reproduce vapor/liquid equilibrium properties. − , More recently, several models that include many-body effects, either implicitly or explicitly, have been proposed. ,,,, An analytical representation of the potential energy surface of the CO 2 dimer (with rigid CO bonds) was derived from reference energies obtained at the symmetry adapted perturbation theory (SAPT) level and used to calculate the second virial coefficient that was found to be in good agreement with the corresponding experimental data . SAPT calculations were also used to develop an implicit many-body model of CO 2 with rigid CO bonds and polarization effects represented by the Drude model .…”

Transferability of data-driven, many-body models for CO2 simulations in the vapor and liquid phases

“…In the last 30 years, several models have been used in molecular simulations for the study of CO 2 and its mixtures. [19][20][21][22][23][24][25][26][27][28][29][30] Early models such as Harris and Yung's EPM/EPM2 models, 19 Potoff and Siepmann's TraPPE model, 20 and Potoff and Panagiotopoulos' exponential-6 model 21 were constructed by fitting to experimental vapor-liquid equilibrium properties. These models generally perform well for bulk thermodynamic and transport properties of CO 2 .…”