Effect of pressure on the resonant multiphonon Raman scattering inUO2

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

“…The computed ratio of zero and high-frequency dielectric constant e 0 /e 1 is in satisfactory agreement with experiments. The calculated Gruneisen constant of the LO mode is found to be substantially lower than that of the TO mode, as observed experimentally [53].…”

“…The calculated values of the lattice parameter, bulk modulus, and elastic constants compare well with the experimentally obtained data [52,53] as given in Table 2. The values of the optically active Raman and infrared frequencies and their Gruneisen constants are given in Table 3.…”

Raman spectroscopy characterization of actinide oxides (U1−yPuy)O2: Resistance to oxidation by the laser beam and examination of defects

“…6 and 7b) depending on the zone selected, with a very intense 645 cm À1 peak or sometimes two contributions at 579 and 639 cm À1 . The 579 cm À1 peak could be attributed to two sources by analogy with UO 2 [18,20]: the 1LO phonon frequency, or degenerate phonons found at similar energies but induced by disorder and irradiation. In each case the 639-645 cm À1 peak had the highest intensity after the T 2g peak, unlike the other lightly damaged samples.…”

“…4a have recently been assigned to 1LO and 2LO phonons. It must be remembered that although the origin of the 1150 cm À1 band is still debated in the literature [17][18][19][20][21][22], it is of interest to monitor this band as an indicator of the extent of UO 2 oxidation. Its intensity drops considerably for minor differences in stoichiometry [17].…”

“…1). Before sintering, the powder was heat treated in oxygen depleted in 18 O to enhance 16 O-18 O isotopic exchange and thus considerably reduce neutron emissions by (a,n) reaction. At the moment of fabrication the pellet geometric density was 9.2 g cm À3 (i.e.…”