Electrostatic and induction effects in the solubility of water in alkanes

D. Asthagiri, Arjun Valiya Parambathu, Deepti Ballal, Walter G. Chapman

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Experiments show that at 298 K and 1 atm pressure, the transfer free energy, μex, of water from its vapor to liquid normal alkanes CnH2n+2 (n=5...12) is negative. Earlier it was found that with the united-atom TraPPE model for alkanes and the SPC/E model for water, one had to artificially enhance the attractive alkane-water cross interaction to capture this behavior. Here we revisit the calculation of μex using the polarizable AMOEBA and the non-polarizable Charmm General (CGenFF) forcefields. We test both the AMOEBA03 and AMOEBA14 water models; the former has been validated with the AMOEBA alkane model while the latter is a revision of AMOEBA03 to better describe liquid water. We calculate μex using the test particle method. With CGenFF, μex is positive and the error relative to experiments is about 1.5 kBT. With AMOEBA, μex is negative and deviations relative to experiments are between 0.25 kBT (AMOEBA14) and 0.5 kBT (AMOEBA03). Quantum chemical calculations in a continuum solvent suggest that zero point effects may account for some of the deviation. Forcefield limitations notwithstanding, electrostatic and induction effects, commonly ignored in consideration of water-alkane interactions, appear to be decisive in the solubility of water in alkanes.

Original languageEnglish
Article number074506
JournalJournal of Chemical Physics
Volume147
Issue number7
DOIs
StatePublished - Aug 21 2017
Externally publishedYes

Funding

D.A., A.V.P., W.G.C. are grateful for the financial support from the Robert A. Welch Foundation (Grant No. C-1241), the Rice University Consortium for Processes in Porous Media (Houston, TX, USA), and the Abu Dhabi National Oil Company (ADNOC). D.B. was supported by the Division of Material Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract No. W-7405-430 ENG-82 with Iowa State University. We thank B. Xue, D. B. Harwood, and J. I. Siepmann for their comments on Ref. 7 that led us to correct that work8 and focus on the vapor-to-liquid transfer process. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

FundersFunder number
D.A.
U.S. Department of EnergyW-7405-430, 7, W-7405-430 ENG-82
Welch FoundationC-1241
Office of ScienceDE-AC02-05CH11231
Basic Energy Sciences
Advanced Scientific Computing Research
Rice University
Iowa State Universitywork8
Center for Environmental Sciences and Engineering
Robert A. and Renee E. Belfer Family Foundation
Apple University Development Fund, Apple University Consortium
Abu Dhabi National Oil Company

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