arXiv subjects

D. Yesilleten

Publications and source records attributed to D. Yesilleten.

3 recordsLinked to original sources

arXiv2000

New physics of grain boundaries in bcc metals from the atomic level: molybdenum as a case study

We present a systematic trend study of the symmetric tilt grain boundaries about the <110> axis in molybdenum. Our results show that multiple structural phases, some incorporating vacancies, compete for the boundary ground state. We find that at low external stress vacancies prefer to bind to the boundaries in high concentrations, and moreover, that external stress drives structural phase transitions which correspond to switching the boundaries on and off as pipe-diffusion pathways for vacancies. Finally, we present physical arguments which indicate these phenomena are likely to occur in the other bcc transition metals as well.

cond-mat.mtrl-sci↗

arXiv1998

The Hopgrid algorithm: multilevel synthesis of multigrid and wavelet theory

The multigrid algorithm is a multilevel approach to accelerate the numerical solution of discretized differential equations in physical problems involving long-range interactions. Multiresolution analysis of wavelet theory provides an efficient representation of functions which exhibit localized bursts of short length-scale behavior. Applications such as computing the electrostatic field in and around a molecule should benefit from both approaches. In this work, we demonstrate how a novel interpolating wavelet transform, which in itself is the synthesis of finite element analysis and wavelet theory, may be used as the mathematical bridge to connect the two approaches. The result is a specialized multigrid algorithm which may be applied to problems expressed in wavelet bases. With this approach, interpolation and restriction operators and grids for the multigrid algorithm are predetermined by an interpolating multiresolution analysis. We will present the new method and contrast its efficiency with standard wavelet and multigrid approaches.

physics.comp-ph↗

arXiv1998

The stabilizing role of itinerant ferromagnetism in inter-granular cohesion in iron

We present a simple, general energy functional for ferromagnetic materials based upon a local spin density extension to the Stoner theory of itinerant ferromagnetism. The functional reproduces well available ab initio results and experimental interfacial energies for grain boundaries in iron. The model shows that inter-granular cohesion along symmetric tilt boundaries in iron is dependent upon strong magnetic structure at the interface, illuminates the mechanisms underlying this structure, and provides a simple explanation for relaxation of the atomic structure at these boundaries.

cond-mat.mtrl-sci↗