Localized electronic and vibrational states in amorphous diamond

Amorphous diamond structures with more than 97% of sp3 bonding fraction are generated by quenching liquid carbon using tight-binding molecular-dynamics simulations. The electronic and vibrational properties of the amorphous sample are investigated.

Guest-induced reversible crystal-to-amorphous-to-crystal transformation in a Co(ii)-based metal–organic framework

A crystal-to-amorphous-to-crystal (CAC) transformation was obtained during the dehydration/rehydration process. Moreover, an amorphous sample DPPB-2 could separate methanol and ethanol from other VOCs.

Process-dependent reversible mechanochromic luminescence of bismuth based polymorphs

The reversibility of the mechanochromic luminescence (MCL) properties of bismuth based polymorphs depends on how the ground amorphous sample is treated.

The local structure and crystallization of FeB nanoparticle

Using molecular dynamics simulation, we have studied the structural evolution of FeB nanoparticle under annealing and the physical properties of its polymorphs such as crystalline, amorphous and mixed samples. The main focus of present work is the crystallization mechanism and the local structure of polymorphs of FeB nanoparticle. The simulation result shows that the amorphous sample undergoes the crystallization via the nucleation mechanism. During the crystallization, B atoms move out the places where the Fe crystal locates, and diffuse to the boundary region of Fe crystal. The crystal growth proceeds when this boundary region attains specific properties which are defined by the fraction of B atoms and the energies of AB -atoms and CB -atoms. Further our study indicates that unlike amorphous sample, the crystalline and mixed samples consist of three distinct parts including Fe crystalline and two FeB amorphous parts ( B -poor and B -rich amorphous part). The different polymorphs of FeB nanoparticle differ in the local structure, size of Fe crystal and energies of different type atoms.

Discussion on Relationship between Viscosities of Molten Zr-Cu Based Alloys and their Glass Forming Ability

The dynamic viscosities of molten Zr55Ni5Al10Cu30 and Zr50Cu50 alloys were measured by using rotating cylinder method under non-vacuum condition. According to the lnη~1/T curves, discontinuous changes were found and the activation energy was calculated. The activation energy of molten Zr55Ni5Al10Cu30 alloy is obviously larger than that of molten Zr50Cu50 alloy. Amorphous sample of Zr55Ni5Al10Cu30 with 3mm diameter was prepared successfully under non-vacuum condition, but there are crystallization phases in Zr50Cu50 amorphous sample with 2mm diameter. The relationship between viscosities of molten Zr-Cu based alloys and their glass forming ability (GFA) was discussed, and viscosities of molten Zr-Cu based alloys play an important role on their GFA.

Combination of EXAFS and Differential Anomalous X-ray Scattering for Studying Ni 2 Zr Amorphous Alloy

In this paper we report a first application of the new idea of combining EXAFS and differential anomalous scattering techniques to obtain partial distribution functions for a binary amorphous sample. This method has been successfully employed in extracting Ni-Ni and Ni-Zr pair distribution functions for Ni2Zr prepared by mechanical alloying. A comparison with results from previous studies is also reported.

A fitting method for the determination of crystallinity by means of X-ray diffraction

A best-fitting version of the X-ray diffraction method of Gehrke & Zachmann [Makromol. Chem. (1981). 182, 627–635] for crystallinity determination, which is a modification of the method developed by Ruland [Acta Cryst. (1961). 14, 1180–1185], is presented. The data, corrected and normalized to electron units (e.u.), are plotted as I(s)s 2 vs s and fitted by pseudo-Voigt functions for the crystalline peaks added to a background scattering IB (s)s 2, with IB (s) = (1 − Xc )I am(s) + Xc 〈f(s)2〉[1 − exp(−ks 2)], where I am is the experimental intensity of a completely amorphous sample (also corrected and normalized to e.u.), 〈f(s)2〉 is the mean square atomic scattering factor in the material, Xc is the degree of crystallinity and k is a factor which includes either thermal or lattice disorder, where s = 2(sin θ)/λ. The use of the scattering of the amorphous sample in this non-integral form of the Ruland equations overcomes the problem, encountered with other procedures, of locating the continuous (background) scattering with accuracy. The degree of crystallinity and the disorder factor are supplied directly by the optimization process. Furthermore, the line broadening analysis which allows the determination of crystallite size is automatically obtained as a by product. Samples of polyethylene terephthalate (PET) with different degrees of crystallinity are investigated. The results are compared with those obtained by other methods which do not use fitting techniques.