The response to compression of the synthetic zeolite Li-ABW (LiAlSiO4 · H2O, Z = 4, s.g. Pna21) w... more The response to compression of the synthetic zeolite Li-ABW (LiAlSiO4 · H2O, Z = 4, s.g. Pna21) was explored by synchrotron X-ray powder diffraction experiments, using silicone oil as non-penetrating pressure transmitting medium, and Car Parrinello Molecular Dynamics simulations. In the range Pamb – 8.9 GPa, a nearly isotropic compression for the axial parameters and a cell volume decrease of approximately 12% are observed. A discontinuity in the cell parameters vsP behaviour can be detected between 5 and 6 GPa. As a consequence, the bulk modulus was calculated separately in the Pamb – 4.9 GPa and 5.6–8.9 GPa pressure ranges. The corresponding values (72(2) GPa and 80(2) GPa, respectively) are among the highest found up to now for zeolites studied with non-penetrating P-transmitting media. Molecular Dynamics simulations were performed at volumes corresponding to Pamb, 1.5, 5.6, and 7.6 GPa, respectively. At 1.5 GPa the channel system is already elliptically deformed, and the zig-zag trend of the 4-ring tetrahedral chains is enhanced. Moreover, the water molecule chain running along the channel becomes interrupted and the water molecules are more strongly connected to the framework oxygen atoms. The four-fold coordination of Li cation is maintained up to the highest pressure and only a slight bond distance decrease is observed above 1.5 GPa. In the Pamb – 5.6 GPa range, all T–O–T angles decrease with pressure, and hence the Li-ABW structure can be defined as collapsible. Otherwise, at higher compression, average T–O–T angles increase slightly. Overall, the deformation of the Li-ABW upon compression resembles that achieved by anhydrous Li-ABW in the high temperature regimes.
... The samples were embedded in epoxy resin and polished with diamond paste. ... The three sampl... more ... The samples were embedded in epoxy resin and polished with diamond paste. ... The three samples with high content of K 2 O can be classified as mixed-alkali glass – or low-magnesium high-potassium glass – typical of the Final Bronze Age period, whereas most of the other ...
Abstract The thermal behavior of Na-as synthesized and NH 4 exchanged samples of ECR-1 has been s... more Abstract The thermal behavior of Na-as synthesized and NH 4 exchanged samples of ECR-1 has been studied by synchrotron radiation powder diffraction. The temperature resolved experiments were performed in capillary using a translating imaging plate system. The ...
Negli ultimi anni si è assistito ad un notevole sviluppo e diffusione delle ricerche archeometric... more Negli ultimi anni si è assistito ad un notevole sviluppo e diffusione delle ricerche archeometriche con un crescente numero di materiali archeologici studiati mediante metodologie di indagine fisica e chimica. I quesiti relativi ad oggetti di interesse storico-archeologico posti da storici dell’arte e archeologi riguardano in genere: la composizione dell’oggetto, la sua provenienza e la provenienza delle materie prime, la sua datazione, la tecnologia che ha portato alla sua produzione e il suo stato di conservazione. La ricerca archeometrica prevede che, una volta poste in luce le problematiche storico archeologiche, venga definito il protocollo scientifico da utilizzare ovvero che vengano definite le tecniche appropriate per fornire la caratterizzazione degli oggetti. Intrinsecamente legata alla scelta della tecnica analitica appropriata, è la scelta delle metodologia di campionamento; in relazione alla disponibilità di materiale prelevabile o alla necessità di preservare l’integri...
The response to compression of the synthetic zeolite Li-ABW (LiAlSiO4 · H2O, Z = 4, s.g. Pna21) w... more The response to compression of the synthetic zeolite Li-ABW (LiAlSiO4 · H2O, Z = 4, s.g. Pna21) was explored by synchrotron X-ray powder diffraction experiments, using silicone oil as non-penetrating pressure transmitting medium, and Car Parrinello Molecular Dynamics simulations. In the range Pamb – 8.9 GPa, a nearly isotropic compression for the axial parameters and a cell volume decrease of approximately 12% are observed. A discontinuity in the cell parameters vsP behaviour can be detected between 5 and 6 GPa. As a consequence, the bulk modulus was calculated separately in the Pamb – 4.9 GPa and 5.6–8.9 GPa pressure ranges. The corresponding values (72(2) GPa and 80(2) GPa, respectively) are among the highest found up to now for zeolites studied with non-penetrating P-transmitting media. Molecular Dynamics simulations were performed at volumes corresponding to Pamb, 1.5, 5.6, and 7.6 GPa, respectively. At 1.5 GPa the channel system is already elliptically deformed, and the zig-zag trend of the 4-ring tetrahedral chains is enhanced. Moreover, the water molecule chain running along the channel becomes interrupted and the water molecules are more strongly connected to the framework oxygen atoms. The four-fold coordination of Li cation is maintained up to the highest pressure and only a slight bond distance decrease is observed above 1.5 GPa. In the Pamb – 5.6 GPa range, all T–O–T angles decrease with pressure, and hence the Li-ABW structure can be defined as collapsible. Otherwise, at higher compression, average T–O–T angles increase slightly. Overall, the deformation of the Li-ABW upon compression resembles that achieved by anhydrous Li-ABW in the high temperature regimes.
... The samples were embedded in epoxy resin and polished with diamond paste. ... The three sampl... more ... The samples were embedded in epoxy resin and polished with diamond paste. ... The three samples with high content of K 2 O can be classified as mixed-alkali glass – or low-magnesium high-potassium glass – typical of the Final Bronze Age period, whereas most of the other ...
Abstract The thermal behavior of Na-as synthesized and NH 4 exchanged samples of ECR-1 has been s... more Abstract The thermal behavior of Na-as synthesized and NH 4 exchanged samples of ECR-1 has been studied by synchrotron radiation powder diffraction. The temperature resolved experiments were performed in capillary using a translating imaging plate system. The ...
Negli ultimi anni si è assistito ad un notevole sviluppo e diffusione delle ricerche archeometric... more Negli ultimi anni si è assistito ad un notevole sviluppo e diffusione delle ricerche archeometriche con un crescente numero di materiali archeologici studiati mediante metodologie di indagine fisica e chimica. I quesiti relativi ad oggetti di interesse storico-archeologico posti da storici dell’arte e archeologi riguardano in genere: la composizione dell’oggetto, la sua provenienza e la provenienza delle materie prime, la sua datazione, la tecnologia che ha portato alla sua produzione e il suo stato di conservazione. La ricerca archeometrica prevede che, una volta poste in luce le problematiche storico archeologiche, venga definito il protocollo scientifico da utilizzare ovvero che vengano definite le tecniche appropriate per fornire la caratterizzazione degli oggetti. Intrinsecamente legata alla scelta della tecnica analitica appropriata, è la scelta delle metodologia di campionamento; in relazione alla disponibilità di materiale prelevabile o alla necessità di preservare l’integri...
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