Liquid chloroform structure from computer simulation with a fullab initiointermolecular interaction potential

Yin, Chih-Chien; Li, Arvin Huang-Te; Chao, Sheng D.

doi:10.1063/1.4829760

“…Bromine-bromine RDF (Fig. 1, bottom-left plot) reflects that, contrary to our previous work (4.2 Å), OPLS FF Structure of liquid TCM has been recently studied by Pothoczki et al 63 , while MD simulations and ab initio calculations for the same system have been performed by Yin et al 64 . Figure 2 presents plots of RDFs based on the simulations using OPLS FF performed for TCM.…”

Section: A Structural Analysis Of Studied Liquidsmentioning

confidence: 68%

“…These observations indicate that the first shell is not reproduced by the used force field, while the second one is substantially overestimated. This behaviour rises from the short range H-H and C-H interactions that are part of the repulsive potential region 64 . These interactions were not included in the fitting procedure of OPLS FF that relies more on fitting thermochemical properties 50 .…”

Section: A Structural Analysis Of Studied Liquidsmentioning

confidence: 97%

Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

Vasquez¹,

Dybała-Defratyka

²

2020

Preprint

0

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Very often in order to understand physical and chemical processes taking place among several phases fractionation of naturally abundant isotopes is monitored. Its measurement can be accompanied by theoretical determination to provide a more insightful interpretation of observed phenomena. Predictions are challenging due to the complexity of the effects involved in fractionation such as solvent effects and non-covalent interactions governing the behavior of the system which results in the necessity of using large models of those systems. This is sometimes a bottleneck and limits the theoretical description to only a few methods. In this work vapour pressure isotope effects on evaporation from various organic solvents (ethanol, bromobenzene, dibromomethane, and trichloromethane) in the pure phase are estimated by combining force field or self-consistent charge density-functional tight-binding (SCC-DFTB) atomistic simulations with path integral principle. Furthermore, the recently developed Suzuki-Chin path integral is tested. In general, isotope effects are predicted qualitatively for most of the cases, however, the distinction between position-specific isotope effects observed for ethanol was only reproduced by SCC-DFTB, which indicates the importance of using non-harmonic bond approximations. Energy decomposition analysis performed using the symmetry-adapted perturbation theory (SAPT) revealed sometimes quite substantial differences in interaction energy depending on whether the studied system was treated classically or quantum mechanically. Those observed differences might be the source of different magnitudes of isotope effects predicted using these two different levels of theory which is of special importance for the systems governed by non-covalent interactions.

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“…The most frequent orientation observed in the liquid was not very probable in the gas phase, and the strongest dimer was relatively rare in the liquid phase, indicating that for these systems, the molecule pair interactions cannot be simply used to predict the structures expected in the liquid phase. These examples show that for molecular liquids consisting of quasi spherical molecules, more effective theoretical methods such ab initio molecular dynamics simulations or improved ab initio force-fields [105,106] are necessary.…”

Section: Discussionmentioning

confidence: 99%

Intermolecular Interaction in Methylene Halide (CH2F2, CH2Cl2, CH2Br2 and CH2I2) Dimers

Almásy

¹

,

Bende

²

2019

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The intermolecular interaction in difluoromethane, dichloromethane, dibromomethane, and diiodomethane dimers has been investigated using high level quantum chemical methods. The potential energy curve of intermolecular interaction along the C⋯C bond distance obtained using the coupled-cluster theory with singles, doubles, and perturbative triples excitations CCSD(T) were compared with values given by the same method, but applying the local (LCCSD(T)) and the explicitly correlated (CCSD(T)-F12) approximations. The accuracy of other theoretical methods—Hartree–Fock (HF), second order Møller–Plesset perturbation (MP2), and dispersion corrected DFT theory—were also presented. In the case of MP2 level, the canonical and the local-correlation cases combined with the density-fitting technique (DF-LMP2)theories were considered, while for the dispersion-corrected DFT, the empirically-corrected BLYP-D and the M06-2Xexchange-correlation functionals were applied. In all cases, the aug-cc-pVTZ basis set was used, and the results were corrected for the basis set superposition error (BSSE) using the counterpoise method. For each molecular system, several dimer geometries were found, and their mutual orientations were compared with the nearest neighbor orientations obtained in recent neutron scattering studies. The nature of the intermolecular interaction energy was discussed.

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“…Structure of liquid TCM has been recently studied by Pothoczki et al 63 , while MD simulations and ab initio calculations for the same system have been performed by Yin et al 64 . Figure 2 presents plots of RDFs based on the simulations using OPLS FF performed for TCM.…”

Section: A Structural Analysis Of Studied Liquidsmentioning

confidence: 99%

Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

Vásquez¹,

Dybała-Defratyka²

2020

Preprint

0

View full text Add to dashboard Cite

Very often in order to understand physical and chemical processes taking place among several phases fractionation of naturally abundant isotopes is monitored. Its measurement can be accompanied by theoretical determination to provide a more insightful interpretation of observed phenomena. Predictions are challenging due to the complexity of the effects involved in fractionation such as solvent effects and non-covalent interactions governing the behavior of the system which results in the necessity of using large models of those systems. This is sometimes a bottleneck and limits the theoretical description to only a few methods. In this work vapour pressure isotope effects on evaporation from various organic solvents (ethanol, bromobenzene, dibromomethane, and trichloromethane) in the pure phase are estimated by combining force field or self-consistent charge density-functional tight-binding (SCC-DFTB) atomistic simulations with path integral principle. Furthermore, the recently developed Suzuki-Chin path integral is tested. In general, isotope effects are predicted qualitatively for most of the cases, however, the distinction between position-specific isotope effects observed for ethanol was only reproduced by SCC-DFTB, which indicates the importance of using non-harmonic bond approximations. Energy decomposition analysis performed using the symmetry-adapted perturbation theory (SAPT) revealed sometimes quite substantial differences in interaction energy depending on whether the studied system was treated classically or quantum mechanically. Those observed differences might be the source of different magnitudes of isotope effects predicted using these two different levels of theory which is of special importance for the systems governed by non-covalent interactions.

show abstract

Liquid chloroform structure from computer simulation with a fullab initiointermolecular interaction potential

Cited by 18 publications

References 68 publications

Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

Intermolecular Interaction in Methylene Halide (CH2F2, CH2Cl2, CH2Br2 and CH2I2) Dimers

Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

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