Mechanical heterogeneity in ionic liquids

Autor(es)

Veldhorst, Arno A. ^[1] ; Ribeiro, Mauro C. C. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Lab Espectroscopia Mol, Dept Quim Fundamental, Inst Quim, Av Prof Lineu Prestes 748, BR-05508000 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Chemical Physics; v. 148, n. 19 MAY 21 2018.
• Citações Web of Science: 5

Resumo

Molecular dynamics (MD) simulations of five ionic liquids based on 1-alkyl-3-methylimidazolium cations, {[}C(n)C(1)im](+), have been performed in order to calculate high-frequency elastic moduli and to evaluate heterogeneity of local elastic moduli. The MD simulations of {[}C(n)C(1)im]{[}NO3], n = 2, 4, 6, and 8, assessed the effect of domain segregation when the alkyl chain length increases, and {[}C(8)C(1)im]{[}PF6] assessed the effect of strength of anion-cation interaction. Dispersion curves of excitation energies of longitudinal and transverse acoustic, LA and TA, modes were obtained from time correlation functions of mass currents at different wavevectors. High-frequency sound velocity of LA modes depends on the alkyl chain length, but sound velocity for TA modes does not. High-frequency bulk and shear moduli, K infinity and G infinity, depend on the alkyl chain length because of a density effect. Both K infinity and G infinity are strongly dependent on the anion. The calculation of local bulk and shear moduli was accomplished by performing bulk and shear deformations of the systems cooled to 0 K. The simulations showed a clear connection between structural and elastic modulus heterogeneities. The development of nano-heterogeneous structure with increasing length of the alkyl chain in {[}C(n)C(1)im]{[}NO3] implies lower values for local bulk and shear moduli in the non-polar domains. The mean value and the standard deviations of distributions of local elastic moduli decrease when {[}NO3](-) is replaced by the less coordinating {[}PF6](-) anion. Published by AIP Publishing. (AU)

• Processo FAPESP: 12/13119-3 - Espectroscopia vibracional em fases condensadas
• Beneficiário: Mauro Carlos Costa Ribeiro
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 14/13134-8 - Estudo por simulação computacional de heterogeneidade de stress em líquidos iônicos
• Beneficiário: Arnold Adriaan Veldhorst
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado