Low-energy phonon dispersion in LaFe₄Sb₁₂

We studied the vibrational dynamics of a single crystal of LaFe 4Sb 12 by three-axis inelastic neutron spectroscopy. The dispersion of phonons with wave vectors q along [xx0] and [xxx] directions in the energy range of eigenmodes with high amplitudes of lanthanum vibrations, i.e., at planckomegalsim12 meV is identified. Symmetry-avoided anticrossing dispersion of phonons is established in both monitored directions and distinct eigenstates at high-symmetry points and at the Brillouin-zone center are discriminated. The experimentally derived phonon dispersion and intensities are compared with and backed up by ab initio lattice dynamics calculations. Results of the computer model match well with the experimental data

Effect of the electropositive elements A = Sc, La, and Ce on the microscopic dynamics of AV₂Al₂₀

We report on the inelastic response of AV(2)Al(20) (with A - Sc, La and Ce) probed by high-resolution inelastic neutron scattering experiments. Intense signals associated with the dynamics of Sc, La and Ce are identified in the low-energy range at 6-14 meV in ScV2Al20 and at 8-16 meV in LaV2Al20 and CeV2Al20. Their response to temperature changes between 2 and 300 K reveals a very weak softening of the modes upon heating in LaV2Al20 and CeV2Al20 and a distinguished blue shift by about 2 meV in ScV2Al20. By means of density functional theory (DFT) and lattice dynamics calculations (LDC) we show that the unusual anharmonicity of the Sc-dominated modes is due to the local potential of Sc featured by a strong quartic term. The vibrational dynamics of ScV2Al20 as well as of LaV2Al20 and CeV2Al20 is reproduced by a set of eigenmodes. To screen the validity of the DFT and LDC results they are confronted with data from X-ray diffraction measurements. The effect of the strong phonon renormalization in ScV2Al20 on thermodynamic observables is computed on grounds of the LDC derived inelastic response. To set the data in a general context of AV(2)Al(20) compounds and their physical properties we report in addition computer and experimental results of the binary V2Al20 compound

Single Cell Analytics for NanoBiology

Anselmetti D, Griemla N, Hellmich W, et al. Single Cell Analytics for NanoBiology. NanoBiotechnology. 2005;1(3):267-270