Using MD snapshots in ab initio and DFT calculations: OH vibrations in the first hydration shell around Li+(aq)
2005 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 109, no 23, 5144-5152 p.Article in journal (Refereed) Published
The average OH stretching vibrational frequency for the water molecules in the first hydration shell around a Li+ ion in a dilute aqueous solution was calculated by a hybrid molecular dynamics + quantum-mechanical (MD + QM) approach. Using geometry configurations from a series of snapshots from an MD simulation, the anharmonic, uncoupled OH stretching frequencies were calculated for 100 first-shell OH oscillators at the B3LYP and HF/6-31G(d,p) levels of theory, explicitly including the first shell and the relevant second shell water molecules into charge-embedded supermolecular QM calculations. Infrared intensity-weighting of the density-of-states (DOS) distributions by means of the squared dipole moment derivatives (which vary by a factor of 20 over the OH stretching frequency band at the B3LYP level), changes the downshift from approximately -205 to -275 cm(-1) at the B3LYP level. Explicit inclusion of relevant third-shell water molecules in the supermolecular cluster leads to a further downshift by approximately -30 cm-1. Our final estimated average downshift is approximately -305 cm-1. The experimental value lies somewhere in the range between - 290 and -420 cm-1. Also, the absolute nu(OH) frequency is well reproduced in our calculations. In-liquid instantaneous correlation curves between nu(OH) and various typical H-bond strength parameters such as R((OO)-O-...), R((HO)-O-...), the intramolecular OH bond length, and the IR intensity are presented. Some of these correlations are robust and persist also for the rather distorted instantaneous geometries in the liquid; others are less so.
Place, publisher, year, edition, pages
2005. Vol. 109, no 23, 5144-5152 p.
aluminum(iii) chloride solution, molecular-dynamics simulations, liquid water, aqueous-solutions, geometry optimization, infrared-spectroscopy, ionic hydration, hdo molecules, monte-carlo, spectrum
IdentifiersURN: urn:nbn:se:kth:diva-14832ISI: 000229751600023OAI: oai:DiVA.org:kth-14832DiVA: diva2:332873
QC 201005252010-08-052010-08-05Bibliographically approved