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Establishing Consistent van der Waals Volumes of Polyatomic Ions from Crystal Structures
Author(s) -
Beichel Witali,
Eiden Philipp,
Krossing Ingo
Publication year - 2013
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300659
Subject(s) - van der waals force , van der waals radius , polyatomic ion , ion , chemistry , arrhenius equation , volume (thermodynamics) , counterion , van der waals strain , crystal structure , crystal (programming language) , ansatz , thermodynamics , crystallography , molecule , physics , activation energy , organic chemistry , quantum mechanics , computer science , programming language
Based on temperature ( T ) dependent crystal structure data of seven organic salts, a radii‐based scheme for the calculation of the van der Waals volume ( V vdw ) is analyzed. The obtained volumes ( V vdw,r , r =radius‐based) are nearly T independent. An ion volume partitioning scheme is proposed by fixing the anion volumes of [Cl] − , [Br] − , [I] − , [BF 4 ] − , [PF 6 ] − , [OTf] − and [NTf 2 ] − . The van der Waals volumes ( V vdw,r +/− ) of 48 ions are established, with low standard deviations (0.2–3.6 Å 3 , 0.1–4.5 % of V vdw,r +/− ). The ion volumes are independent of the counterion and one crystal structure already suffices for their derivation. Correlations of the viscosity with V vdw,r via a Litovitz ansatz and our recently derived Arrhenius‐type approach prove that these volumes are suitable for the volume‐based description and prediction of IL properties. The corresponding correlation coefficient for the latter is R 2 =0.86 for 40 ILs (354 data points) in the T range of 253–373 K.