1. Department of Physics; H.P.T. Arts and R.Y.K. Science College; Nasik Maharashtra - 422 005 (India
2. Condensed Matter Theory Group, Department of Physics and Astronomy; Uppsala University; Box 516 S-75120 Uppsala (Sweden
3. Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH); S-100 44 Stockholm (Sweden
4. Centre for Theoretical and Computational Molecular Science, Australian Institute for Bioengineering and Nanotechnology; The University of Queensland; Brisbane Qld 4072 (Australia