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Title: Vibrations and relaxations in network-forming glasses
Author: Haar, A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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The vibrations of the glasses SiO2, GeO2, GeS2, GeSe2 and ZnCl2 were investigated by Raman scattering in particular in the boson-peak region. Furthermore, to test for a correlation between boson peak and first sharp diffraction peak, five samples of amorphous As2S3 quenched from different temperatures were investigated by neutron diffraction. The vibrational dynamics of amorphous GeO2 was furthermore investigated very much in detail by neutron scattering on the instrument MARI, and with special emphasis on the low-frequency dynamics, on the instruments IN6 and DN6. On the latter two instruments, the vibrational dynamics of GeSs and GeS2 were also investigated. A method for determining the partial mean-square displacement of a binary glass from the momentum-transfer dependence of the modes is presented, and it is suggested that employing the incoherent approximation in unsuitable regions can help discern peak positions. A further special point to note is the similarity of the momentum-transfer dependence of the modes and the static structure factor up to frequencies of 24meV. Concentrating on the temperature dependence of the low-frequency dynamics, glassy As2S3 was investigated by neutron scattering on the instruments IN6 and MIBEMOL from far below the glass-transition to close to the boiling point. A point of special interest is the persistence of the first sharp diffraction peak to the highest temperature investigated. The study of relaxational dynamics was done on the glass formers As2S3I1.65, As2S3, and As2S3Ge0.85 that were ascertained to be an intermediate, a strong, and a very strong (like SiO2) glass former, respectively, interpreting the results of penetration and plane-plate viscosity measurements from 1012Pa s down to 104Pa s.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available