Ab initio all-electron full-potential linearized augmented plane-wave method for one-dimensional systems
In recent years we have witnessed an enormous progress in the chemicalsynthesis and the development of technology allowing the fabrication of a rich variety of one-dimensional (1D) structures.They include single walled (SWNT) and multi-walled (MWNT) one-dimensional tubular structures, made of carbon, GaN, BN, TiO, VO and other compounds, thin metallic quantum wires, quasi-1D molecular magnets etc, and show a variety of new intriguing physical phenomena.In order to understand the structure-property relation in these new materials on the basis of the electronic structure, ab-initio calculations basedon the density functional theory play an important role.In this work we have presented an extension of the full-potential linearized augmented plane-wave (FLAPW) method to truly one-dimensional systems. The space is partitioned into three regions, the muffin-tin sphere around the atom, a vacuum region surrounding a cylinder and the interstitial region betweenthe atoms and the vacuum region. In each region optimal basis functions for the wavefunctions, charge density and potential are used. Despite theplane-wave representation in the interstitial region we were able to include a wide class of chiral symmetries, characteristic for one-dimensional systems. The one-dimensional FLAPW method was implemented as extension of the FLAPW code FLEUR and parallelized for supercomputing applications. Due to the efficiently adjusted basis functions and partitioning of space, the 1D code allows to achieve a significant speed-up, for instance, approximately by a factor of 150 for monowires, as compared to the super-cell approach in the bulk code.The accuracy, precision and correctness of the code was validated on a set of 1D structures, already calculated previously with other methods. We focused on the systems of a large current interest in the field of nanophysics. We reported on the calculations of 3d- and 4d- monowires (Ti; Y, Zr, Nb, Mo, Tc,Ru, Rh and Pd). For these monowires we investigated the ferro- and antiferromagnetic instability, calculated equilibrium interatomic distances, spin and orbital moments, magnetocrystalline anisotropy energies. We found that across the 4d-transition-metal series, Y and Nb exhibit a nonmagneticground-state, Mo and Tc are antiferromagnetic and Zr, Ru, Rh and Pd are ferromagnetic. For the Ru, Rh and Pd system is was found that the easy axis isperpendicular to the wire for Ru and Pd and along-the-wire for Rh. Further we considered a (6,0) nanowire of gold atoms, and a hybrid structure of an iron monowire inside a gold (6,0) tube, showing that the Fe monowire is prone to the Peierls dimerization. For the hybrid system Fe@Au(6,0) we found a high spin-polarization at the Fermi level, proposing, therefore, this system as a possible candidate for spin-dependent transport applications. Using a super-cell approach within the one-dimensional FLAPW method we investigated a set of one-dimensional multiple-decker sandwiches of benzene and vanadium, which are for the past 20 years of great interest in the field of organometallics. The calculated structural results obtained are in good agreement with experimental and theoretical results. After the calculation oftotal energies, magnetic moments, orbital interaction schemes, one can finally conclude, that with the increasing number of the vanadium atoms in the molecule, the magnetic moments of vanadii prefer to order ferromagnetically, which was recently observed experimentally.
info:eu-repo/classification/ddc/530, Physik, density functional theory, one-dimensional nanostructures, magnetism, electronic properties, planewaves
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