1,106 research outputs found
Phase stability, ordering tendencies, and magnetism in single-phase fcc Au-Fe nanoalloys
Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but
L1 and L1 orderings were reported in single-phase Au-Fe nanoparticles.
Motivated by these observations, we study the structural and ordering
energetics in this alloy by combining density functional theory (DFT)
calculations with effective Hamiltonian techniques: a cluster expansion with
structural filters, and the configuration-dependent lattice deformation model.
The phase separation tendency in Au-Fe persists even if the fcc-bcc
decomposition is suppressed. The relative stability of disordered bcc and fcc
phases observed in nanoparticles is reproduced, but the fully ordered L1
AuFe, L1 AuFe, and L1 AuFe structures are unstable in DFT.
However, a tendency to form concentration waves at the corresponding [001]
ordering vector is revealed in nearly-random alloys in a certain range of
concentrations. This incipient ordering requires enrichment by Fe relative to
the equiatomic composition, which may occur in the core of a nanoparticle due
to the segregation of Au to the surface. Effects of magnetism on the chemical
ordering are also discussed.Comment: 23 pages, 11 figure
The development of an algorithm of adaptive discrete PID control for the extruder based on a microcontroller
Projective resolution of irreducible modules over tiled order
We indicate the method for computing the kernels of projective resolution of irreducible module over tiled order. On the base of this method we construct projective resolution of irreducible module and calculate the global dimension of tiled order. The evident view of kernels of projective resolution allows to check easily the regularity of tiled order
Tiled orders of width 3
We consider projective cover over tiled order and calculate the kernel of epimorphism from direct sum of submodules of distributive module to their sum
Large Broadening of the Superconducting Transition by Fluctuations in a 3D Metal at High Magnetic Fields: The MgB case
It is shown that the transition to the low temperature superconducting state
in a 3D metal at high magnetic field is smeared dramatically by thermal
fluctuation of the superconducting order parameter. The resulting
superconducting-to-normal crossover occurs in a vortex liquid state which is
extended well below the mean-field . Application to MgB yields
good quantitative agreement with recently reported data of dHvA oscillation in
the superconducting state
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