A combined molecular dynamic simulation and X-ray absorption spectroscopy to investigate the atomistic solvation structure of cation in poly(vinyl alcohol):potassium thiocyanate (KSCN) solid electrolytes

Molecular dynamic (MD) simulation and extended X-ray absorption fine structure (EXAFS) spectroscopy were combined to investigate the atomistic solvation structures of poly(Vinyl Alcohol):potassium thiocyanate (PVA:KSCN) solid electrolytes. The radial distribution functions (RDFs) calculated from MD simulation with COMPASS forcefield give structural parameters such as K+-O and K+-H distances, coordination numbers (N) and Debye-Waller factor (only from configurational disorder part). For PVA:KSCN (K+:O molar ratio = 1:20) system, the RDFs of the first solvation shell around K+ ions consist mainly of oxygen atoms from PVA chain with an average K+-O distance and coordination number (N) of 2.57 Å and 4.8 atoms, respectively. A direct comparison between MD-EXAFS and experimental EXAFS spectra gives an overall good agreement for both frequency and amplitude of the oscillations over the wide k range (2.0 < k < 11.0 Å− 1). Agreement in the frequencies of oscillations implies that the K+-O distances from experiment and simulation data are almost the same. However, the experimental EXAFS spectra have a broader peak compared to the MD-EXAFS spectra. The Debye-Waller factor determined from MD-EXAFS (0.0183 Å2) is smaller than that of the experimental spectra (0.0204 Å2).