The magnetic properties of small Cr clusters on Fe surfaces have been investigated using a self-consistent noncollinear spd tight-binding method, parametrized through ab initio tight-binding linear muffin-tin orbital results. A competition between antiferromagnetic coupling within the cluster and antiferromagnetic coupling with the Fe surface has been found, leading to noncollinear magnetic arr...

An electronic orbital of a dihedral angle of a molecular chain is introduced. A tight-binding Hamiltonian on the basis of the dihedral orbitals is defined. This yields the Green’s function between two dihedral angles of the chain. It is revealed that the Green’s function, which we refer to as the electronic communicability, is useful in differentiating protein molecules of different types of co...

Bending induced deformations in single walled carbon nanotubes with zigzag and armchair chirality have been studied computationally using a classical molecular dynamics simulation method. In this the interatomic forces have been described with Brenner’s empirical model potential. The results given by this classical model have been assessed by letting the most critical, i.e. the most deformed pa...

We present a method for total energy minimizations and molecular dynamics simulations based either on tight-binding or on Kohn-Sham hamiltonians. The method leads to an algorithm whose computational cost scales linearly with the system size. The key features of our approach are (i) an orbital formulation with single particle wavefunctions constrained to be localized in given regions of space, a...

We consider energy-minimizing divergence-free eigenfields of the curl operator in dimension three from the perspective of contact topology. We give a negative answer to a question of Etnyre and the first author by constructing curl eigenfields which minimize L energy on their co-adjoint orbit, yet are orthogonal to an OVERTWISTED contact structure. We conjecture that K-contact structures on S-b...

This is an example for the application of the LCAO method to bandstructure calculation. We will apply this method to a two-dimensional sheet of graphite, called graphene, and carbon nanotubes, which are slices of graphene rolled into a seamless cylinder. Graphene and carbon nanotubes (CN) have peculiar electronic properties, which can be derived by the LCAO method (also called tight-binding met...

A self-consistent environment-dependent tight binding method is presented that was developed to simulate eigenvalue spectra, electron densities and Coulomb potential distributions for hydrocarbon systems. The method builds on a non-selfconsistent environment-dependent tight binding model for carbon [Tang et al., Phys. Rev. B 53, 979 (1996)] with parameters added to describe hydrocarbon bonds an...

Ultra-precision machining of metals, the breaking of nanowires under tensile stress and fracture of nanoscale materials are examples of technologically important processes which are both extremely difficult and costly to investigate experimentally. We describe a multiscale method for the simulation of such systems in which the energetically active region is modelled using a robust tight-binding...