Birabar Ranjit Kumar Nanda

Using density functional calculations we explore the possibilities of inducing spin moments in otherwise non-magnetic electronic structure of graphene. Through intercalation of H, N, O and F atoms between two hexagonal stacked graphene layers, we show that unpaired electrons can be generated when the planar coordinates of the functional atoms coincide with the center of the graphene hexagon. The spin-half states are realized at the functional sites for certain values of interlayer separations. For oxygen and fluorine these interlayer separations represent the natural stable phases and for hydrogen and nitrogen they induce instability which can be overcome by applying external pressure. We attribute the formation of spin-half states to the one dimensional confinement potential exerted by the graphene layers on the valence electrons of the functional elements.

Molecular dynamics simulation technique is fairly successful in studying the structural aspects and dynamics of fluids. Here we study the ability of ab initio molecular dynamics (ab initio MD) to carry out virtual experiments to synthesize new crystalline materials and to predict their structures. For this purpose the olivine phosphate LiFePO4 (LFPO) is used as an example. As transition metal oxides in general are stabilized with layered geometry, we carried out ab initio MD simulations over a hypothetical layered configuration consisting of alternate LiPO2 and FeO2 layers. With intermittent steps of electron minimization, the resulted equilibrium lattice consist of PO4 tetrahedra and distorted Fe-O complexes similar to the one observed in the experimental lattice.

We demonstrate the simultaneous optical trapping and magnetic manipulation of Fe-doped upconverting particles to achieve full control over six-degrees of freedom of a rigid body in optical tweezers, and the precise detection of its motion.