Characterization of structure and dynamics of an aqueous scandium(iii) ion by an extended ab initio QM/MM molecular dynamics simulation |
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Authors: | Viwat Vchirawongkwin Chinapong Kritayakornupong Anan Tongraar Bernd M Rode |
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Affiliation: | Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand. |
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Abstract: | Hydration structure and dynamics of an aqueous Sc(iii) solution were characterized by means of an extended ab initio quantum mechanical/molecular dynamical (QM/MM) molecular dynamics simulation at Hartree-Fock level. A monocapped trigonal prismatic structure composed of seven water molecules surrounding scandium(iii) ion was proposed by the QM/MM simulation including the quantum mechanical effects for the first and second hydration shells. The mean Sc(iii)-O bond length of 2.14 ? was identified for six prism water molecules with one capping water located at around 2.26 ?, reproducing well the X-ray diffraction data. The Sc(iii)-O stretching frequency of 432 cm(-1) corresponding to a force constant of 130 N m(-1), evaluated from the enlarged QM/MM simulation, is in good agreement with the experimentally determined value of 430 cm(-1) (128 N m(-1)). Various water exchange processes in the second hydration shell of the hydrated Sc(iii) ion predict a mean ligand residence time of 7.3 ps. |
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