Neutron spectroscopy of H impurity in PdD: Covibrations of the H and D atoms

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2009-01, Vol.80 (13)
• Main Authors: Antonov, Vladimir E., Davydov, A.I., Fedotov, Vladimir K., Ivanov, Alexander S., Kolesnikov, Alexander I, Kuzovnikov, Michael
• Format: Article
• Language: English
• Subjects: ATOMS; DEFECTS; NEUTRON SPECTROSCOPY; NEUTRONS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; SCATTERING; SPECTRA; SPECTROMETERS
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.80.134302

Three powder samples of solid isotopic solutions PdD1 xHx with x = 0.050, 0.072, and 0.091 are prepared under high pressure, and the spectra of their optical vibrations are studied by inelastic neutron scattering (INS) at ambient pressure and 5 K using the high-luminosity IN1-BeF spectrometer at ILL, Grenoble. These spectra are shown to be well represented by a linear combination of a contribution from the undisturbed matrix of stoichiometric PdD and a contribution due to the H impurity. The optical spectrum of PdD consists of a strong peak at 37 meV with a shoulder extending to 65 meV. The spectrum due to the H impurity is composed of a broad peak of defect H modes centered at 68 meV and superimposed on a broad N-shaped feature with a range of negative intensity near 36 meV and a shallow maximum at 45 meV. Simulations using the Born-von K rm n model show that this unusual feature is a result of formation of a new band of optical vibrations of the D and H atoms with equal frequencies (co-vibrations) caused by H-D interaction.