SPONTANEOUS STRAIN VARIATIONS THROUGH THE LOW TEMPERATURE PHASE TRANSITIONS OF DEUTERATED LAWSONITE
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dc.contributor.author | Carpenter M.A. | |
dc.contributor.author | Meyer H.W. | |
dc.contributor.author | Sondergeld P. | |
dc.contributor.author | Marion S. | |
dc.contributor.author | Knight K.S. | |
dc.date.accessioned | 2021-12-17T07:25:34Z | |
dc.date.available | 2021-12-17T07:25:34Z | |
dc.date.issued | 2003 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=27998759 | |
dc.identifier.citation | American Mineralogist, 2003, 88, 4, 534-546 | |
dc.identifier.issn | 0003-004X | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/33542 | |
dc.description.abstract | High resolution neutron powder diffraction has been used to determine lattice parameter variations of deuterated lawsonite across the Cmcm ↔ Pmcn and Pmcn ↔ P21cn phase transitions, in the temperature interval 1.6–505 K. The variations are reversible through heating and cooling cycles. Strain analysis, based on a displacive model of the transitions with saturation temperatures to describe the temperature-independent behavior as T → 0 K, shows that the data are consistent with a tricritical transition at 271 ± 2 K and a second-order transition at 155 ± 1 K. Comparisons with strains from published dilatation data for a natural (hydrogenated) sample highlight aspects of the transitions that are most dependent on the behavior of protons in the structure. Replacing H by D causes the low temperature transition point to be increased by ~27 K and an anomaly in the strain evolution of the Pmcn transition to increase from ~225 to ~250 K. The transition point of the high-temperature transition remains the same within ± ~2 K. We conclude that proton ordering and displacive contributions are both important in the 271 K transition, though with the displacive component providing the initial symmetry-breaking mechanism. Structural changes that are more dependent on the behavior of H or D become important ~20–50 K below this. Strains for the Pmcn ↔ P21cn transition are consistent with a transition driven by a single order parameter. The data are used to determine values for strain/order parameter coupling coefficients for calculation of elastic anomalies due to the phase transitions. | |
dc.title | SPONTANEOUS STRAIN VARIATIONS THROUGH THE LOW TEMPERATURE PHASE TRANSITIONS OF DEUTERATED LAWSONITE | |
dc.type | Статья |
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