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A study by computational simulation of ionic liquids stress heterogeneity

Grant number: 14/13134-8
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): October 01, 2014
Effective date (End): September 30, 2016
Field of knowledge:Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
Principal Investigator:Mauro Carlos Costa Ribeiro
Grantee:Arnold Adriaan Veldhorst
Home Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:12/13119-3 - Vibrational spectroscopy in condensed phases, AP.TEM


The microscopic structure of a molten salt is determined by particle packing with constraint of charge ordering, but the complex molecular structure of large and asymmetric organic ions in the so-called ionic liquids adds new structural motifs not seen in simple molten salts. The intermediate range order observed as a first sharp diffraction peak at kFSDP ~ 0.5 Å-1 in the static structure factor of ionic liquids is the result of nanoscale structural heterogeneity of polar and non-polar domains. In this work, we will investigate whether the segregation of domains imply a corresponding segregation of stiff and soft domains in the ionic liquid. This will be accomplished by the calculation of local atomic stresses in molecular dynamics simulation of ionic liquids. This calculation will allow us to compare instantaneous mechanical properties of ionic liquids and the wavevector dependent acoustic excitations in the THz frequency range. Ionic liquids with different length of the alkyl chain in the cation will be simulated because of the effect on nanoscale heterogeneity. The anions will be also varied because the strength of anion-cation interactions has a significant effect on the sound velocity of ionic liquids. This work also aims to disentangle thermal and free volume effects on the high-frequency mechanical properties, so that the ionic liquids will be simulated in different temperature and pressure conditions. The results of this work will contribute to our understanding on the relationship between elastic constants and long-time structural relaxation of glass-forming liquids.

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
VELDHORST, ARNO A.; RIBEIRO, MAURO C. C. Mechanical heterogeneity in ionic liquids. Journal of Chemical Physics, v. 148, n. 19 MAY 21 2018. Web of Science Citations: 5.
VELDHORST, ARNO A.; FARIA, LUIZ F. O.; RIBEIRO, MAURO C. C. Local solvent properties of imidazolium-based ionic liquids. JOURNAL OF MOLECULAR LIQUIDS, v. 223, p. 283-288, NOV 2016. Web of Science Citations: 5.

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