Electronic Structures of Framework‐Substituted Type‐I Tin Clathrate Semiconductors.
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| Title: | Electronic Structures of Framework‐Substituted Type‐I Tin Clathrate Semiconductors. |
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| Authors: | Xue, Dong1 (AUTHOR) dxue@lfnu.edu.cn, Deng, Yanbin2 (AUTHOR), Myles, Charles W.3 (AUTHOR), Bai, Yulong (AUTHOR) ylbai@imu.edu.cn |
| Source: | Advances in Condensed Matter Physics. 4/29/2026, Vol. 2026, p1-12. 12p. |
| Subjects: | Electronic structure, Clathrate compounds, Band gaps, Density functional theory, Bulk modulus, Semiconductors, Chemical stability |
| Abstract: | Density functional theory (DFT) calculations within the local density approximation (LDA) method were employed to investigate the electronic structure and tuning mechanisms of framework‐substituted Type‐I tin–based clathrates. The calculation reveals that Ga (or Al) preferentially occupies Wyckoff 6c crystallographic sites, whereas the remaining framework‐substituted atoms reside at 16i sites, significantly enhancing the material stability. For K8Ga8Sn38, we investigated two configurations involving a Ga–Ga‐bond‐free structure (i) and a Ga–Ga‐bond‐maximized variant (ii). Configuration (ii) is energetically disfavored because of the asymmetric bond strength distribution within the Ga‐centered tetrahedral sp3 network. The structural effects of guest and framework substitution in the Rb8Al8Sn38 clathrate were studied. K2Rb6Al8Sn38, formed by substituting K for Rb in dodecahedra, increased the bulk modulus B0 to 46.092 GPa versus 43.369 GPa for Rb8Al8Sn38, indicating enhanced cage‐guest size matching and rigidity. Concurrent Al‒Sn bond strength recovery offset volume expansion. Conversely, Ga substitution yielding Rb8Ga8Sn38 decreased B0 to 40.955 GPa, revealing poorer size matching and increased strain at larger volumes. The nonmonotonic B0 vs. volume behavior stems from dual effects, including framework bond strength and guest‐cage size matching. All the compounds are semiconductors, with intrinsic bandgaps decreasing as follows: 0.6247 eV (Rb8Ga8Sn38) > 0.6019 eV (Rb8Al8Sn38) > 0.5932 eV (K2Rb6Al8Sn38). This reduction is attributed to Al‐p orbital contributions lowering the conduction band minimum (CBM) and a sharp decrease in the K‐atom density of states (DOS) near the conduction band edge. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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