title: Phonons and thermodynamics of unmixed and disordered Li0.6FePO4.
abstract: The lithium-storage material Li(0.6)FePO(4) was studied by inelastic neutron scattering and differential scanning calorimetry. Li(0.6)FePO(4) undergoes a transformation from a two-phase mixture (heterosite and triphylite) to a disordered solid-solution at 200 degrees C. Phonon densities of states (DOS) obtained from the inelastic neutron scattering were similar for the two-phase sample measured at 180 degrees C and the disordered sample measured at 220 degrees C. The vibrational entropy of transformation is 1.8 +/-0.9 J/(K mol), which is smaller than the configurational entropy difference of approximately 3.1 J/(K mol). The measured enthalpy of the disordering transition was estimated as 2.5 kJ/mol. The phonon data show a small change in lattice dynamics upon disordering.
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA. rstevens@caltech.edu
authors.forename: R
authors.initials: R
authors.lastname: Stevens
authors.forename: J L
authors.initials: JL
authors.lastname: Dodd
authors.forename: M G
authors.initials: MG
authors.lastname: Kresch
authors.forename: R
authors.initials: R
authors.lastname: Yazami
authors.forename: B
authors.initials: B
authors.lastname: Fultz
authors.forename: B
authors.initials: B
authors.lastname: Ellis
authors.forename: L F
authors.initials: LF
authors.lastname: Nazar