Magnetism of Fe clusters embedded in Cu, Ag, and Au fcc matrices: density functional calculations

We present extensive first principles density functional theory (DFT) calculations dedicated to analyze the magnetic properties of small Fen clusters (n = 2,3) embedded in Cu fcc, Ag fcc and Au fcc matrices. We consider several dimers and trimers having different interatomic distances. In all cases the Fe atoms are embedded as substitutional impurities in the metallic network. For the case of the Fe dimers we have considered two magnetic configurations: ferromagnetic (antiferromagnetic), when the atomic magnetic moment of the Fe atoms are parallel (antiparallel) each other. For the case of dimers immersed in Cu and Ag matrices, the ground state corresponds to the ferromagnetic Fe dimer whose interatomic distance is a/√2. For Fe dimer immersed in the Au matrix the ground state corresponds to a ferromagnetic coupling when the interatomic distance is a√(3/2). In the case of the Fe trimers we have considered three or four magnetic configurations, depending on the Fe cluster geometry. For the case of Fe trimer immersed in Cu and Ag matrices we have found that the ground state corresponds to the ferromagnetic trimer forming an equilateral triangle with an interatomic distance equal to a/√2. The ground state for the Fe trimer immersed in the Au matrix corresponds to the ferromagnetic Fe trimer forming a right angle triangle

Visualizing and clustering financial portfolios using internal compositions

Injection molding is a process employed worldwide to manufacture polymer parts. The final properties of the molded part largely depend on the processing conditions used during the manufacturing process. Therefore, it is necessary to develop empirical approaches that help to understand the relationship between the processing conditions and the final properties of the polymer. In this paper we study the effect of the processing conditions of the injection molding process on the Young's modulus of a low-density polyethylene (LDPE). The effect of both the barrel temperature and the mold temperature was investigated using analysis of variance (ANOVA) and the effect of the levels of each parameter was examined using the surface response methodology (SRM). The ANOVA results showed that the mold temperature is the parameter that most significantly impacts the Young's modulus, followed by the barrel temperature, while the combined interaction of both is negligible. SRM showed that the Young's modulus increases with the mold temperature and decreases with the barrel temperature. Based on the SRM, an empirical equation is proposed which can be used to predict the modulus employing only the barrel and mold temperatures. The changes in the microstructure of the injection molded part are discussed in terms of the crystallinity degree. All this was corroborated with X-ray diffraction (XRD) and differential scanning calorimetry (DSC). © 2013 American Chemical Society