The atomic parameter model for the fifth and sixth transition metal quasicrystal alloys(Mc=0.5)

The forming ability of quasicrystal phase has a relationship with the atomic bond factors based on differences in atom size and electron factors.Usually,those factors or their combination are used to describe the forming ability,stability of alloys,etc.In this paper,the quasicrystal alloy forming abilities for the fifth and sixth transition metals(Y,Zr,Nb,Mo,Ru,Rh,Pd and La,Hf,Ta,W,Re,Os,Ir,Pt) based alloys have been studied by the size factor and the atomic parametric function.It has been found that an ell...     

Random Tilings of High Symmetry: I. Mean-Field Theory

We study random tiling models in the limit of high rotational symmetry. In this limit a mean-field theory yields reasonable predictions for the configurational entropy of free boundary rhombus tilings in two dimensions. We base our mean-field theory on an iterative tiling construction inspired by the work of de Bruijn. In addition to the entropy, we consider correlation functions, phason elasticity and the thermodynamic limit. Tilings of dimension other than two are considered briefly.     

Random Tilings of High Symmetry: II. Boundary Conditions and Numerical Studies

We perform numerical studies including Monte Carlo simulations of high rotational symmetry random tilings. For computational convenience, our tilings obey fixed boundary conditions in regular polygons. Such tilings are put in correspondence with algorithms for sorting lists in computer science. We obtain statistics on path counting and vertex coordination which compare well with predictions of mean-field theory and allow estimation of the configurational entropy, which tends to the value 0.568 per vertex in the limit of continuous symmetry. Tilings with phason strain appear to share the same entropy as unstrained tilings, as predicted by mean-field theory. We consider the thermodynamic limit and argue that the limiting fixed boundary entropy equals the limiting free boundary entropy, although these differ for finite rotational symmetry.     

Diurnal cooling for continuous thermal sources under direct subtropical sunlight produced by quasi-Cantor structure

In this paper, an optical radiative cooler with quasi-Cantor structure is theoretically proposed and analyzed. This simple and symmetrically designed optical structure operates upon continuous thermal sources in diurnal subtropical conditions, and its efficiency is much higher than natural cooling, for instance, when operating upon a typical 323.15 K continuous thermal source with a wind speed at 3 m·s~(-1), it can generate a net cooling power of 363.68 W·m~(-2), which is 18.26% higher than that of non-radiative heat exchange(natural cooling) under the same conditions. Additionally, several aspects are considered in its design to ensure a low cost in application, which is of great economical and environmental significance.     

Ti基准晶复相材料电极的电化学储氢性能

通过电弧熔炼和铜辊急冷技术分别制得Ti1.4V0.6Ni准晶材料和V5Ti9Zr26.2Ni38Cr3.5Co1.5Mn15.6Al0.4Sn0.8（VTZN）合金材料,再用球磨法得到Ti1.4V0.6Ni+20%(质量分数)VTZN的复相材料,研究了该复相材料的组织和电化学储氢特性。 结果表明,复相材料的相组成包括正二十面体准晶相（I-phase）、面心立方相（FCC）和体心立方相（BCC）。 复相材料作为镍氢电池负极,在303 K和放电电流密度为30 mA/g条件下,最大放电容量可达310 mA·h/g,放电性能优于Ti1.4V0.6Ni合金负极。     

一维点阵的电子态

本文利用A、B构成序列有不同排列方式,模拟出晶体、孪晶、准晶和无序的一维结构。应用紧束缚模型,对各结构的电子态进行计算研究,系统地分析比较了各序列的电子能谱、态密度、局域度以及波函数图象,得出准晶体结构是一种新的结构,其电子态不同于晶体、孪晶及无序体的电子态等结论。     

A multifractal study of wave functions in 1-D quasicrystals

Using multifractal analysis we study extended, self-similar and non-self-similar type of wave functions in the Fibonacci model. Extended states arising due to commutation of transfer matrices for certain blocks of atoms in quasiperiodic systems are shown to have the same signature as the Bloch states in terms of the singularity spectrum withf(α)=α=1. Numerically, however, the extended states show a typical multifractal behaviour for finite chain lengths. Finite size scaling corrections yield results consistent with that obtained analytically. The self-similar states at the band edges show a multifractal behaviour and they are energy dependent in the case of blocks of atoms arranged in a Fibonacci sequence. For non-self-similar states we obtain a non-monotonic behaviour off(α) as a function of the chain length. We also show that in cases where extended states exist, the cross-over from extended to non-self-similar states in gradual.     

合金成分和冷凝速率对Al-Mn合金中准晶相形成能力和热稳定性的影响(英文)

本文通过DTA和X射线衍射分析,研究了合金成分和冷凝速率对Al_(100-x)Mn_x(x=12.5,13.5,15.75,17.7,20.6和22.3at%)合金中准晶相形成能力和热稳定性的影响。结果表明:当Mn<16at%,准晶二十面体相的形成能力随合金锰含量的增加而增强,当Mn>16at%,合金中出现准晶十边形相,从而削弱了二十面体相的形成能力,当Mn>22at%,二十面体相几乎被完全抑制。准晶十边形相的形成能力随合金锰含量增加而不断增强。提高冷凝速率会增强二十面体相的形成能力。准晶二十面体相和十边形相的晶化温度均随合金锰含量增加而升高,但受冷凝速率的影响很小。