ILMAT5 presentation

LINK to the PRESENTATION

Abstract

In this work [0], we have applied the DFT-based delta Kohn–Sham (ΔKS) method to ion pairs in a vacuum to obtain X-ray pho­toelectron spectra of corresponding ionic liquids (IL). On the example of forty ion pairs, we demonstrate how the core level binding energy (BE) values can be calcu­lated and used to plot theo­retical spectra at a low computational cost. Furthermore, we compare the ΔKS results, 1s Kohn–Sham orbital energies, and atomic charges against the experi­mental X-ray photoelec­tron data. Recently, in connection to the electro­chemical application in the super­capacitors, we have measured spectra for EMImBF4 and EMImB(CN)4 ionic liquids at the carbon–IL interface [1–3]. Other experimental spectra were obtained from the literature [4,5]. Both the ΔKS BE values and the 1s Kohn–Sham orbital energies show a correlation, yet with a different order of the BEs assigned to spe­cific atoms. We find that neither DDEC6 nor Bader charges cor­relate with the experi­mental data. Thus, the DFT calculations of 1s Kohn–Sham orbital energies provide the fastest way of pre­dicting the XPS spectra. However, more detailed experimental studies are required to resolve the right order of the BE values and its rela­tion to the atomistic structure of the ILs. The ΔKS calculations provide the most precise estimations of the BEs. Herewith, they also demand more resources and cause computa­tional difficulties discussed in the presenta­tion. Besides the prediction power, a robust computational method can help in intepre­tating experimental data when the appropriate reference values are either not available nor directly applicable. Thus, the ΔKS method can find its application in various fields of physics and chemistry where the XPS is used for re­solving electronic and geometric structures of pure ILs, their mixtures, and at interfaces.

In this work, we have applied the DFT-based delta Kohn–Sham (ΔKS) method to ion pairs in a vacuum to obtain X-ray pho­toelectron spectra of corresponding ionic liquids (IL). On the example of forty ion pairs, we demonstrate how the core level binding energy (BE) values can be calcu­lated and used to plot theo­retical spectra at a low computational cost. Furthermore, we compare the ΔKS results, 1s Kohn–Sham orbital energies, and atomic charges against the experi­mental X-ray photoelec­tron data. Recently, in connection to the electro­chemical application in the super­capacitors, we have measured spectra for EMImBF4 and EMImB(CN)4 ionic liquids at the carbon–IL interface [1–3]. Other experimental spectra were obtained from the literature [4,5]. Both the ΔKS BE values and the 1s Kohn–Sham orbital energies show a correlation, yet with a different order of the BEs assigned to spe­cific atoms. We find that neither DDEC6 nor Bader charges cor­relate with the experi­mental data. Thus, the DFT calculations of 1s Kohn–Sham orbital energies provide the fastest way of pre­dicting the XPS spectra. However, more detailed experimental studies are required to resolve the right order of the BE values and its rela­tion to the atomistic structure of the ILs. The ΔKS calculations provide the most precise estimations of the BEs. Herewith, they also demand more resources and cause computa­tional difficulties discussed in the presenta­tion. Besides the prediction power, a robust computational method can help in intepre­tating experimental data when the appropriate reference values are either not available nor directly applicable. Thus, the ΔKS method can find its application in various fields of physics and chemistry where the XPS is used for re­solving electronic and geometric structures of pure ILs, their mixtures, and at interfaces.

[0] M. Lembinen, E. Nõmmiste, H. Ers, B. Docampo‐Álvarez, J. Kruusma, E. Lust, V.B. Ivaništšev, Calculation of core‐level electron spectra of ionic liquids, Int. J. Quantum Chem. 120 (2020). https://doi.org/10.1002/qua.26247.

[1] J. Kruusma, A. Tõnisoo, R. Pärna, E. Nõmmiste, I. Tallo, T. Romann, E. Lust, Electrochimica Acta 206 (2016) 419–426.

[2] J. Kruusma, A. Tõnisoo, R. Pärna, E. Nõmmiste, I. Kuusik, M. Vahtrus, I. Tallo, T. Romann, E. Lust, J. Electrochem. Soc. 164 (2017) A3393–A3402.

[3] A. Tõnisoo, J. Kruusma, R. Pärna, A. Kikas, M. Hirsimäki, E. Nõmmiste, E. Lust, J. Electrochem. Soc. 160 (2013) A1084–A1093.

[4] A. Foelske-Schmitz, D. Weingarth, R. Kötz, Surf. Sci. 605 (2011) 1979–1985.

[5] I.J. Villar-Garcia, E.F. Smith, A.W. Taylor, F. Qiu, K.R.J. Lovelock, R.G. Jones, P. Licence, Phys. Chem. Chem. Phys. 13 (2011) 2797–2808.

MD simulation of BMPyrDCA between graphene walls

Simple demonstration of a molecular dynamics simulation of 408 BMPyrDCA ionic pairs between two graphene walls.

Inputs (packmol.inp, STEEP.mdp, RUN.mdp, topol.top) and force field parameters: github.com/vilab-tartu/LOKT.02.048/tree/master/MD_Gr-BMPyrDCA_pbc. The force fields are taken from github: github.com/vladislavivanistsev/RTIL-FF. References are given within the files.

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MD simulation of bulk BMPyrDCA ionic liquid

Simple demonstration of a molecular dynamics simulation of 25 BMPyrDCA ionic pairs in a box.

Inputs (packmol.inp, STEEP.mdp, RUN.mdp, topol.top) and force field parameters: github.com/vilab-tartu/LOKT.02.048/tree/master/MD_BMPyrDCA_box. The force fields are taken from github: github.com/vladislavivanistsev/RTIL-FF. References are given within the files.

Continue reading “MD simulation of bulk BMPyrDCA ionic liquid”

Travel tips

Summer is a great time for research visits, schools as well as vacations. Here is my check list for a safe trip.

  • Passport, ID card and driving license (and a secure place for these documents)
  • A bottle of water (stay hydrated)
  • Cough drops
  • Wet wipes and napkins
  • Something to read or listen (headphones)
  • A notebook or something to write on
  • A scarf or something to protect your neck from cold
  • A cap or something to close your face while sleeping
  • Sunglasses
  • Compression socks
  • Lightweight and water-resistant pair of shoes
  • Some coins and some cash
  • A universal adapter

6th Baltic Electrochemistry Conference

The 6th Baltic Electrochemistry Conference held in Helsinki, Finland during a period of 14-17 June and collects researchers dedicated to the science and technology of electrochemistry around the Baltic. This conference provides a forum for individuals from research organizations and companies to learn about the latest developments in this rapidly evolving field, to discuss with renowned experts and to build their networks in an informal and friendly atmosphere. The conference covers all forms of electrochemistry, including, but not limited to experimental and theoretical aspects of charge transfer at electrochemical interfaces, electrochemical materials science, and electrocatalysis. In addition, emergent technologies like electrodeposition of nanomaterials and functionalized electrodes, and electrochemical nanostructuring feature along with related poster presentation sessions.

I am taking part in these conference with the poster presentation “DFT-based modeling of associates of ionic liquid ions” where discuss the ability of prediction properties of novel type electrolytes by applying the results of the DFT calculations of simpler ionic associates. For this reason, the effect of the self-interaction and dispersion corrections on the results of DFT calculations for 48 ionic associates has been investigated [1]. The magnitude of the corrections strongly depends on the anion choice and especially in the case of halide anions. It is very important to pay particular attention to that fact because ionic liquid mixture with the addition of halides has attracted attention as a possible electrolyte for supercapacitors [2].

[1] I. Lage-Estebanez, A. Ruzanov, J. M. García de la Vega, M. V. Fedorov and V. B. Ivaništšev, Self-interaction error in DFT-based modelling of ionic liquids, Phys. Chem. Chem. Phys., 18 (2016) 2175-2182.

[2] T. Tooming, T. Thomberg, L. Siinor, K. Tõnurist, A. Jänes, E. Lust, A type high capacitance supercapacitor based on mixed room temperature ionic liquids containing specifically adsorbed iodide anions, J. Electrochem.