کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1331145 | 978997 | 2010 | 8 صفحه PDF | دانلود رایگان |
The crystal and electronic structures of α-tetragonal (α-t) boron were investigated by first-principles calculation. Application of a simple model assuming 50 atoms in the unit cell indicated that α-t boron had a metallic density of state, thus contradicting the experimental fact that it is a p-type semiconductor. The presence of an additional two interstitial boron atoms at the 4c site made α-t boron semiconductive and the most stable. The cohesive energy per atom was as high as those of α- and β-rhombohedral boron, suggesting that α-t boron is produced more easily than was previously thought. The experimentally obtained α-t boron in nanobelt form had about two interstitial atoms at the 8i sites. We consider that the shallow potential at 8i sites generates low-energy phonon modes, which increase the entropy and consequently decrease the free energy at high temperatures. Calculation of the electronic band structure showed that the highest valence band had a larger dispersion from Γ to Z than from Γ to X; this indicated a strong anisotropy in hole conduction.
Calculated electron densities of B50 and B50+2B at site 4c (configuration B).Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 183, Issue 7, July 2010, Pages 1521–1528