Abnormal volumetric thermal expansion in the hourglass fermion materials KHgAs and KHgSb

Title
Abnormal volumetric thermal expansion in the hourglass fermion materials KHgAs and KHgSb
Author
조준형
Keywords
SEMIMETAL
Issue Date
2017-03
Publisher
AMER PHYSICAL SOC
Citation
PHYSICAL REVIEW B, v. 95, no. 10, Article no. 104101
Abstract
Using first principles density functional theory calculations combined with quasi-harmonic approximation, we demonstrate that the recently reported nonsymmorphic "hourglass fermion" materials KHgX (X = As, Sb) belong to a type of negative thermal expansion (NTE) material with an abnormal volumetric thermal expansion. It is revealed that the NTE is caused by the peculiar layered structures of KHgAs and KHgSb, composed of alternately arranged alkali metal and Hg-X atomic layers with residual tensions. Specifically, the coefficients of negative thermal expansion (CNTE) of KHgAs and KHgSb can reach up to -2.7 x 10(-6) K-1 and -4.9 x 10(-6) K-1 along the a axis, respectively, as well as a larger volumetric CNTE of -4.98 x 10(-6) K-1 for KHgSb. The analyses of Gruneisen parameters and vibrational modes show that the NTE of KHgX is driven by the cooperation of membrane and tension effects. It is most likely that the weaker bonds in the Hg-X layer and the smaller mass of alkali metal facilitate the membrane and tension effects, therefore producing a large NTE. Our findings offer insights for understanding the underlying mechanism of NTE behavior in the hourglass fermion materials KHgX.
URI
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.104101https://repository.hanyang.ac.kr/handle/20.500.11754/113292
ISSN
2469-9950; 2469-9969
DOI
10.1103/PhysRevB.95.104101
Appears in Collections:
COLLEGE OF NATURAL SCIENCES[S](자연과학대학) > PHYSICS(물리학과) > Articles
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