Ab initio study of low-dimensional Fe-Si nanostructures

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We present ab initio spin-density functional calculations of the electronic and magnetic properties of Fe-Si nanostructures with a geometry varying between a straight linear wires and triangular stripes for different atomic compositions, which vary from purely iron system to nanostructures formed only by silicon atoms. With decreasing tension along the axis of the nanostructure we find a series of transitions first from dimerized to periodic and zigzag wires, then to a planar triangular stripe. The nanostructures containing Fe atom in composition exhibit only single equilibrium geometry for triangular stripes, whereas the pure Si nanostripe can be found in two different equilibrium geometries with different hybridization between s and p orbitals depending on tension along the axis of the nanostructure. Special attention is paid to the nanostructures with same amount of Fe and Si atoms in composition. These nanostructures exhibit also transition of internal ordering of Fe and Si atoms after structural transition from linear to zigzag wire, because the alternating sequence of Fe and Si atoms is preferred in both structures and have to be kept. These structural and compositional changes can be understood on the basis of a density of states and a crystal orbital hamilton population analysis.

We present ab initio spin-density functional calculations of the electronic and magnetic properties of Fe-Si nanostructures with a geometry varying between a straight linear wires and triangular stripes for different atomic compositions, which vary from purely iron system to nanostructures formed only by silicon atoms. With decreasing tension along the axis of the nanostructure we find a series of transitions first from dimerized to periodic and zigzag wires, then to a planar triangular stripe. The nanostructures containing Fe atom in composition exhibit only single equilibrium geometry for triangular stripes, whereas the pure Si nanostripe can be found in two different equilibrium geometries with different hybridization between s and p orbitals depending on tension along the axis of the nanostructure. Special attention is paid to the nanostructures with same amount of Fe and Si atoms in composition. These nanostructures exhibit also transition of internal ordering of Fe and Si atoms after structural transition from linear to zigzag wire, because the alternating sequence of Fe and Si atoms is preferred in both structures and have to be kept. These structural and compositional changes can be understood on the basis of a density of states and a crystal orbital hamilton population analysis.

nanostructures; iron silicide; ab initio; zigzag wire;

03.06.2014

Aalto University School of Science

Helsinki

Atomic structure of nanosystems from first-principles simulations and microscopy experiments, Physics Boat 2014

72–72

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