B/Al掺杂ZnS电子结构的第一性原理研究

用第一性原理的赝势方法,计算了B和Al掺杂ZnS的电子结构差异.根据计算,掺杂时B原子p态在导带底附近形成高度局域态,而Al原子p态则较为离域;B和Al原子的s态均具有较好的离域性.以上结果表明,从获得n型导电性的角度而言,Al掺杂优于B掺杂.     

First-principles investigation of mechanical and electronic properties of LaAg5 Laves phase under pressure

The effects of applied pressure on the structural, mechanical, and electronic properties of LaAg5 compound were investigated employing the first-principles method based on the density functional theory. The mechanical results demonstrated that bulk modulus, shear modulus and Young's modulus presented the linearly increasing dependences on the external pressure; the B/G and Poisson's ratio indicated that La Ag5 compound was a ductile material with central forces in interatomic under pressure from 0 to 40 GPa; the universal anisotropic index was performed to investigate the elastic anisotropic of La Ag5. Additionally, the pressure dependence of the density of states and Mulliken charge were also discussed. The bonding characterization in La Ag5 was composed of metallic, covalent and ionic. The metallic component was derived from free-electron transferring from Ag-s and Ag-d to Ag-p, and from La-s to La-d. The ionic component was due to the charge movement from La to Ag. The covalent was owing to Ag-p-La-d bonding hybridization and Ag-s-Ag-p in the Ag atomic chains. The covalent and ionic bonds were stronger under pressure but there was no significant change in metallic nature.     

Simultaneous nitriding of silicon and aluminum

Conclusions During the high-temperature nitriding of silicon-aluminum mixtures in nitrogen and ammonia the mixture components undergo nitriding separately, first aluminum and then silicon. Aluminum inhibits the nitriding of silicon, shifting the process toward higher temperatures. The inhibition is apparently due to a reaction between the silicon nitride and aluminum, with the formation of aluminum nitride films on the silicon particles. The nitriding of silicon and aluminum in nitrogen results in the formation of a limited solid solution of aluminum in a silicon nitride based on-Si₃N₄.Translated from Poroshkovaya Metallurgiya, No. 7(211), pp. 1–6, July, 1980.     

Diffusion of silicon in aluminum

Interdiffusion coefficients in Al-Si alloys were determined by Matano’s method in the tem-perature range from 753 to 893 K with the couple consisting of pure aluminum and an Al-Si alloy. Temperature dependence of the impurity diffusion coefficients of Si in Al, obtained by extrapolation of the concentration dependence of the interdiffusion coeffi-cient to zero mole fraction of Si, is given by the following equation: DSi/Al = (2.02^+0.97 _-0.66 × 10^-4 exp [-(136 ±3) kJ mol^-1/RT] m²/s. p ] The Kirkendall marker was found to move toward the Si-rich side, indicating that the Si atom diffuses faster than the Al atom in Al-Si alloys. From the interdiffusion coeffi-cient and the marker shift, the intrinsic diffusion coefficients were calculated. The difference in the activation energies (ΔQ) between the impurity diffusion of Si in Al and the self-diffusion of Al was estimated by means of the asymptotic oscillating po-tential and the Le Claire theory. The calculated value of ΔQ is in fair agreement with the experimental value. The vacancy-solute binding energy for Si in Al was also dis-cussed based on the diffusion data. formerly Undergraduate Student, Tohoku University     

Proteins and cells on PEG immobilized silicon surfaces

Functional adhesion of blood and marrow leukemic cells from 14 acute myeloid leukemia patients presenting with hyperleukocytosis was evaluated by performing cytoadhesion assays on purified (extracellular matrix proteins) and non-purified supports (MRC5 fibroblastic cell line). Results, in 30-min chromium release assay, show a mean +/- S.D. adhesion to fibronectin, collagen, and laminin respectively of 30 +/- 17%, 20 +/- 13%, 25 +/- 17% for blood leukemic cells and 18 +/- 11%, 11 +/- 10%, 11 +/- 8% for marrow leukemic cells. These differences between blood and marrow cells were statistically significant (respectively P = 0.005, P = 0.01 and P = 0.002), while no difference was noted regarding adhesion to non-purified supports. The higher adhesion of blood blast cells to purified supports was observed regardless of CD34 expression. No significant difference was observed in the expression of cell surface VLA-molecules (CD29, CD49b, CD49d, CD49e, CD49f) between blood and marrow blast cells. The addition of GM-CSF or G-CSF induced increased adhesion of marrow blasts and decreased adhesion of blood blasts leading to a loss of the difference between blood and marrow cells. In a 60-min chromium release assay, marrow blasts adhered even more than blood leukemic cells to fibronectin. In contrast, marrow blasts from 'aleukemic' acute myeloid leukemia patients did not show any modification regarding their adhesion to extracellular matrix proteins when co-cultured with growth factors.