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Based on the first-principles plane-wave basis pseudopotential calculations, we investigate mechanical properties and electronic structures of the hardest known oxide, cotunnite TiO2. The calculated results show that cotunnite TiO2 has the highest bulk modulus (348 GPa) and hardness (32 GPa) among the high-pressure phases of TiO2, but its mechanical properties are not superior to those of c-BN. Moreover, the high hardness of cotunnite TiO2 can be understood from both the dense crystal structure (high valence electron density and short bond lengths) and the unusual mixtures of covalent and ionic bonding of Ti-O. 相似文献
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Determination of the relative permittivity of the AlGaN barrier layer in strained AlGaN/GaN heterostructures 下载免费PDF全文
Using the measured capacitance--voltage curves and the photocurrent
spectrum obtained from the Ni Schottky contact on a strained
Al_0.3Ga_0.7N/GaN heterostructure, the value of the relative
permittivity of the AlGaN barrier layer was analysed and calculated
by self-consistently solving Schr?dinger's and Poisson's
equations. It is shown that the calculated values of the relative
permittivity are different from those formerly reported, and reverse
biasing the Ni Schottky contact has an influence on the value of the
relative permittivity. As the reverse bias increases from 0 V to
--3~V, the value of the relative permittivity decreases from 7.184
to 7.093. 相似文献
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