AIMD Results for a Concentrated Solution of Tetra-ethylammonium Tetra-fluoroborate in Propylene Carbonate

Ab initio molecular dynamics (AIMD) calculations are implemented for a concentrated solution of tetra-ethylammonium tetra-fluoroborate in propylene carbonate (TEABF₄/PC), which is of interest in electrochemical double-layer capacitors. AIMD calculations predict more sharply structured ion-ion center partial radial distributions than either GAFF or OPLS-aa force-fields in classic FFMD calculations. This may be due to AIMD refinement of van der Waals interactions which drive ion-pairing and phase separation of TEABF₄ from PC at this elevated concentration. Quantifying the charge transfer of BF₄^- and N(CH₂CH₃)₄⁺ ions to neighboring solution species, the (Bader) partial charges of BF₄^- and N(CH₂CH₃)₄⁺ ions in PC solution differ from the formal charges by being smaller in magnitude by about 5%.