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The interaction of H, H2, and MgH2 with graphene is investigated using the density functional theory to explore the possibility of exploiting graphene or functionalized graphene as a hydrogen storage medium. The H atom is positioned at various distances from the graphene surface and the energetics are computed in detail. The extent of interaction of the s electron of H with graphene's pz electrons is well brought out. Similar investigations are carried out for H2, MgH2. In the case of H atom, a HC covalent bond is formed. This process turns out to be a prerequisite for proton transfer through graphene. Interactions of H2 and MgH2 with graphene are different from that of H. It leads to the conclusion that functionalized graphene will better substrate/candidate for applications like hydrogen storage. [ABSTRACT FROM AUTHOR]

The antiferromagnetic phase of a 2‐D Wigner crystal is investigated, using a localized representation for electrons. In our model, the electrons are located at the lattice sites of a face‐centered square lattice (corresponding to bcc in the 3‐D case). This lattice may be thought of as consisting of two equivalent interpenetrating sublattices. The ground‐state energies of the antiferromagnetic phase of a 2‐D Wigner electron crystal are computed with uniform neutralizing, Gaussian‐type, and Yukawa‐type positive backgrounds in the range of rs = 5 to 130. The role of correlation energy is suitably taken into account. The possibility of the antiferromagnetic phase of the 2‐D Wigner crystal having a square or circle as the region of occupation in momentum space is also analyzed. The low‐density region favorable for the antiferromagnetic phase of Wigner crystallization is found to be at rs = 7.0. Our results agree well with experimental and other theoretical results for the 2‐D Wigner crystal. The structure‐dependent Wannier functions, which give proper localized representation for Wigner electrons, are constructed and employed in the calculation for the first time. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]