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Hossain F.M.,University Center for Mass and Thermal Transport in Engineering Materials | Dlugogorski B.Z.,University of Newcastle | Kennedy E.M.,University of Newcastle | Belova I.V.,University Center for Mass and Thermal Transport in Engineering Materials | Murch G.E.,University Center for Mass and Thermal Transport in Engineering Materials
Solid State Communications | Year: 2010

The electronic, optical and bonding properties of MgCO3 (magnesite, rhombohedral calcite-type structure) are calculated using a first-principles density-functional theory (DFT) method considering the exchange-correlation function within the local density approximation (LDA) and the generalized gradient approximation (GGA). The indirect band gap of magnesite is estimated to be 5.0 eV, which is underestimated by ∼1.0 eV. The fundamental absorption edge, which indicates the exact optical transitions from occupied valence bands to the unoccupied conduction band, is estimated by calculating the photon energy dependent imaginary part of the dielectric function using scissors approximations (rigid shift of unoccupied bands). The optical properties show consistent results with the experimental calcite-type structure and also show a considerable optical anisotropy of the magnesite structure. The density of states and Mulliken population analyses reveal the bonding nature between the atoms. © 2010 Elsevier Ltd. All rights reserved. Source


Fiedler T.,University Center for Mass and Thermal Transport in Engineering Materials | Belova I.V.,University Center for Mass and Thermal Transport in Engineering Materials | Murch G.E.,University Center for Mass and Thermal Transport in Engineering Materials
Computational Materials Science | Year: 2010

For the first time, a newly developed Lattice Monte Carlo (LMC) method is used to determine concentration profiles for combined mass diffusion and chemical reaction. Different chemical reaction models are considered: instantaneous reaction, irreversible reaction and reversible reaction. Several simple problems are addressed so that LMC solutions can be compared to exact analytical and numerical reference solutions. Excellent agreement between analytical solutions and numerical results is obtained. In addition, a more complex scenario is considered in order to present the capability of the new method. © 2009 Elsevier B.V. All rights reserved. Source


Fiedler T.,University Center for Mass and Thermal Transport in Engineering Materials | Belova I.V.,University Center for Mass and Thermal Transport in Engineering Materials | Broxtermann S.,University Center for Mass and Thermal Transport in Engineering Materials | Murch G.E.,University Center for Mass and Thermal Transport in Engineering Materials
Computational Materials Science | Year: 2012

This paper addresses the thermal analysis of self-propagating high temperature synthesis (SHS) in joining operations of temperature sensitive materials. A parametric finite element analysis of SHS is conducted, i.e. the influence of reaction rate, ignition temperature and reaction zone thickness on reaction stability and velocity is investigated. Special regard is given to surrounding materials such as amorphous alloys in joining operations. These materials act as heat sinks that conduct energy away from the reaction zone and thus diminish or even extinguish the reaction. In addition to the numerical simulation, analytical relations are developed to introduce criteria for reaction stability. Analytical and numerical results are compared for verification. © 2011 Elsevier B.V. All rights reserved. Source

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