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Spectrochim Acta A Mol Biomol Spectrosc. 2006 Sep;65(1):44-50. Epub 2006 Jul 10.

Vibrational spectroscopic investigation of structurally-related LiFePO4, NaFePO4, and FePO4 compounds.

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  • 1Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Room 208, Norman, 73019, USA.

Abstract

Vibrational spectroscopy was utilized to investigate the local structure of LiFePO(4), NaFePO(4), and FePO(4). The factor group splitting of the intramolecular PO(4)(3-) vibrations is between 10 and 20 cm(-1) less for NaFePO(4) than for LiFePO(4). This is because Li(+) ions have a higher charge density than Na(+) ions and can form stronger coordinative bonds with the PO(4)(3-) anions. Thus, the internal modes are more perturbed in LiFePO(4) and exhibit larger factor group splitting effects. The similarity of the factor group multiplets for both LiFePO(4) and NaFePO(4), particularly the PO(4)(3-) bending modes, strongly suggests that the 506 and 470 cm(-1) bands of LiFePO(4) consist almost entirely of lithium translatory motion. There are marked differences between the vibrational spectrum of FePO(4) and those of LiMPO(4) (M=Mn, Fe, Co, or Ni) or NaFePO(4). The monovalent cations interact with the oxygen atoms of the phosphate groups, affecting the frequencies and intensities of the intramolecular PO(4)(3-) modes, in a manner that is absent in FePO(4).

PMID:
16829170
[PubMed - indexed for MEDLINE]
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