Novikov VV, Matovnikov AV, Mitroshenkov NV, Kornev BI, Pilipenko KS, Likhanov MS, Shevelkov AV. Structural irregularities and peculiarities of low-temperature thermal properties of Sn
24P
19.4Br
8 clathrate.
Dalton Trans 2017;
46:9110-9117. [PMID:
28664972 DOI:
10.1039/c7dt01196b]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Temperature changes of the heat capacity and unit cell parameters of Sn24P19.4Br8 clathrate were experimentally determined in the temperature range of 2 to 300 K. The data obtained were analyzed using Debye-Einstein approximation and taking into account the impact of both disorder in the host matrix and the presence of vacancies in the framework. Anomalous negative contribution to the thermal expansion was revealed and related to the defect mode influence on the clathrate thermal properties as a result of vibrations of two-level systems (TLS). The guest atoms that have the opportunity to occupy spatially close yet energetically non-equivalent positions in the asymmetric environment of the host matrix atoms play a principal role in the TLS formation. The results are compared with those previously obtained for semiclathrate Ge31P15Se8.
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