480 research outputs found
Prototiles and Tilings from Voronoi and Delone cells of the Root Lattice A_n
We exploit the fact that two-dimensional facets of the Voronoi and Delone
cells of the root lattice A_n in n-dimensional space are the identical
rhombuses and equilateral triangles respectively.The prototiles obtained from
orthogonal projections of the Voronoi and Delaunay (Delone) cells of the root
lattice of the Coxeter-Weyl group W(a)_n are classified. Orthogonal projections
lead to various rhombuses and several triangles respectively some of which have
been extensively discussed in the literature in different contexts. For
example, rhombuses of the Voronoi cell of the root lattice A_4 projects onto
only two prototiles: thick and thin rhombuses of the Penrose tilings. Similarly
the Delone cells tiling the same root lattice projects onto two isosceles
Robinson triangles which also lead to Penrose tilings with kites and darts. We
point out that the Coxeter element of order h=n+1 and the dihedral subgroup of
order 2n plays a crucial role for h-fold symmetric aperiodic tilings of the
Coxeter plane. After setting the general scheme we give examples leading to
tilings with 4-fold, 5-fold, 6-fold,7-fold, 8-fold and 12-fold symmetries with
rhombic and triangular tilings of the plane which are useful in modelling the
quasicrystallography with 5-fold, 8-fold and 12-fold symmetries. The face
centered cubic (f.c.c.) lattice described by the root lattice A_(3)whose
Wigner-Seitz cell is the rhombic dodecahedron projects, as expected, onto a
square lattice with an h=4 fold symmetry.Comment: 22 pages, 17 figure
Scattering in abrupt heterostructures using a position dependent mass Hamiltonian
Transmission probabilities of the scattering problem with a position
dependent mass are studied. After sketching the basis of the theory, within the
context of the Schr\"{o}dinger equation for spatially varying effective mass,
the simplest problem, namely, tranmission through a square well potential with
a position dependent mass barrier is studied and its novel properties are
obtained. The solutions presented here may be adventageous in the design of
semiconductor devices.Comment: Eur. Phys. J. B. To be publishe
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