Simplified Generation of the Input Models of Object Oriented Micromagnetic Framework (OOMMF)

Object Oriented MicroMagnetic Framework (OOMMF) is a micromagnetic simulation tool. It takes a memory initialization file (MIF) as the input and outputs various forms of data such as data table, graph and magnetic configuration plots. It is accurate and fast compared to other existing tools such as MATLAB. Few experimentalists used it in the past, however, due to two main reasons. First, OOMMF requires a specific version of programming environment on the local computer which is difficult to be installed. Second, MIF file is very complicated to code and it also requires users to read a lengthy guidelines. Our solution to these problems is to first install OOMMF on nanoHUB, and second design a MIF generator, which is a separate tool can help users to design their models without understanding how to code a MIF file. By using the MIF generator, a user can enter the parameters of their micromagnetic models, such as dimensions and magnetic fields, and generates a corresponding MIF file which can be loaded into OOMMF as an input for further simulation. As a result, both the MIF generator and OOMMF are published onto nanoHUB so users can run all simulations on a web-based browser. Two different experiments were simulated to prove the success of this project. A cubic micromagnet was simulated in both local and nanoHUB OOMMF and the simulation results are nearly identical. Also, two cylindrical nanowires were modeled through the MIF generator and simulated in OOMMF. The simulation results correspond to the experimental results obtained before. Overall, OOMMF is improved by designing a separate tool which helps users to generator input files for OOMMF

nanoHUB.org: A Gateway to Undergraduate Simulation-Based Research in Materials Science and Related Fields

Our future engineers and scientists will likely be required to use advanced simulations to solve many of tomorrow\u27s challenges in nanotechnology. To prepare students to meet this need, the Network for Computational Nanotechnology (NCN) provides simulation-focused research experiences for undergraduates at an early point in their educational path, to increase the likelihood that they will ultimately complete a doctoral program. The NCN summer research program currently serves over 20 undergraduate students per year who are recruited nationwide, and selected by NCN and the faculty for aptitude in their chosen field within STEM, as well as complementary skills such as coding and written communication. Under the guidance of graduate student and faculty mentors, undergraduates modify or build nanoHUB simulation tools for exploring interdisciplinary problems in materials science and engineering, and related fields. While the summer projects exist within an overarching research context, the specific tasks that NCN undergraduate students engage in range from modifying existing tools to building new tools for nanoHUB and using them to conduct original research. Simulation tool development takes place within nanoHUB, using nanoHUB’s workspace, computational clusters, and additional training and educational resources. One objective of the program is for the students to publish their simulation tools on nanoHUB. These tools can be accessed and executed freely from around the world using a standard web-browser, and students can remain engaged with their work beyond the summer and into their careers. In this work, we will describe the NCN model for undergraduate summer research. We believe that our model is one that can be adopted by other universities, and will discuss the potential for others to engage undergraduate students in simulation-based research using free nanoHUB resources

Observation of an oxygen isotope effect in YBa\u3csub\u3e2\u3c/sub\u3eCu\u3csub\u3e3\u3c/sub\u3eO\u3csub\u3e7\u3c/sub\u3e

A small decrease in Tc of 0.3 K to 0.5 K is observed when as much as 90% of the 16O in YBa2Cu3O7 is substituted with18O. This result is consistent with our observation that there is an oxygen isotope effect in La1.85Sr0.15CuO4, but in contrast with previous reports that there is no isotope effect for YBa2Cu3O7. This new result suggests that phonons play an important role in the electron-pairing mechanism in YBa2Cu3O7

Observation of an Isotope Shift in the Superconducting Transition Temperature of La\u3csub\u3e1.85\u3c/sub\u3eSr\u3csub\u3e0.15\u3c/sub\u3eCuO\u3csub\u3e4\u3c/sub\u3e

An oxygen isotope shift is observed in superconducting La1.85Sr0.15CuO4 when 18O is substituted partially for 16O; the superconducting transition temperature Tc is lowered by 0.3 to 1.0 K in different samples. We examine these results using conventioanl phonon-mediated BCS theory and conclude that, for La1.85Sr0.15CuO4, phonons play an important role in the pairing mechanism

Absence of the Metal-Support Interaction for Ni/TiO\u3csub\u3e2\u3c/sub\u3e Composites Prepared Using Ion-Exchange Techniques

Many recent reports on the surface properties of transition-metalcatalysts dispersed on high surface area oxide supports have shown that the support can alter markedly the intrinsic activity of the metal. In particular, when group 8-10 metals are supported on reducible metal oxides, the surface chemistry and the electronic properties of the composite depend on the reduction temperature used for pretreatment. For example, the chemisorption of H2 at room temperature on metal-TiO2 composites decreases sharply as the reduction temperature used to prepare the catalyst is increased from 573 to 773 K. This change in surface chemistryhas been attributed to a strong interaction between the metal andthe TiOx(x \u3c 2). By understanding the conditions required to induce this interaction, the acitivity and selectivity of supported metal catalysts can be tailored for specific applications. In this paper, we show that the extent of the interaction can be controlled if the composition at the interface between the nickel and Ti02 is manipulated by varying the method used to disperse the nickel

Surface Chemistry of Nickel Supported on Ti\u3csub\u3en\u3c/sub\u3eO\u3csub\u3e2n-1\u3c/sub\u3e

Small metal particles dispersed on inorganic oxides are among the most important heterogeneous catalysts. While the primary function of the oxide support is to increase the metal surface area, these supports can cause pronounced changes in the catalytic and chemisorption properties of the metal. In particular, metals supported on TiO2, have attracted attention due to the observation that activity and selectivity for Fischer-Tropsch synthesis can be altered, depending on the temperature a t which the metal Ti02 composite is reduced. Furthermore, H2 and CO chemisorption are suppressed for composites reduced at higher temperatures. In this paper, we show that the stoichiometry of the TiOx, support has a large influence on the surface chemistry of the metal