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The interaction and diffusion of lithium atoms in a (5,5) carbon nanotube is studied using density-functional theory. The Li-nanotube interaction perpendicular to the tube axis for a single Li inside and outside the tube is calculated and compared with the Li-graphene interaction obtained using the same technique. Both interactions are similar in the repulsive region but exhibit differences in their attractive part. Nevertheless, they can be described using a common parametrization. The Li-Li interaction is calculated as a function of their separation inside the tube. This interaction is similar to a screened repulsive Coulomb potential at small separations. However, at larger separations, the Li-Li interaction does not vanish and shows residual oscillations. This repulsive long-ranged interaction favors concerted diffusion of many Li atoms compared to the independent diffusion of individual Li inside the tube. The interaction and diffusion of lithium atoms in a ͑5,5͒ carbon nanotube is studied using density-functional theory. The Li-nanotube interaction perpendicular to the tube axis for a single Li inside and outside the tube is calculated and compared with the Li-graphene interaction obtained using the same technique. Both interactions are similar in the repulsive region but exhibit differences in their attractive part. Nevertheless, they can be described using a common parametrization. The Li-Li interaction is calculated as a function of their separation inside the tube. This interaction is similar to a screened repulsive Coulomb potential at small separations. However, at larger separations, the Li-Li interaction does not vanish and shows residual oscillations. This repulsive long-ranged interaction favors concerted diffusion of many Li atoms compared to the independent diffusion of individual Li inside the tube. Disciplines Engineering | Materials Science and Engineering Comments

Density functional theory has been used to analyse the interaction between sulfuric acid and graphene. Four different coverages, ranging from a nearly isolated sulfuric acid molecule (one H2SO4 molecule per 32 C atoms) to a bilayer (one H2SO4 molecule per 4 C atoms) have been studied calculating geometries, binding energies, charge transfers and band structures. The results show that there is protonation of the graphene sheet by the acid, in accordance with experimental results for H2SO4 adsorbed onto highly oriented pyrolytic graphite and for single-wall carbon nanotubes in concentrated sulfuric acid. Nevertheless the electronic structure of graphene is not heavily affected and its zero-band-gap semiconducting behaviour is preserved. As the coverage increases, the acid molecules rotate approaching their orientation in the pure crystal, showing that graphene can template the growth of a sulfuric acid crystal.

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A nonlocal exchange energy functional developed within the weighted spin-density approximation (WSDA) and a local Coulomb correlation energy functional are combined within the densityfunctional scheme for the calculation of the electronic structure of many-electron systems. Both functionals include alternative forms of the pair-correlation functions governing the size and shape of the Fermi and Coulomb holes. Self-consistent calculations have been performed for all atoms from He to Rn within the exchange-only USDA scheme. These have been compared to the results of similar calculations using Becke s exchange functional. Besides, the results of calculations for all atoms from He to Ar, including both exchange and correlation, are compared with those of the self-interaction-corrected method. In addition to obtaining accurate total, exchange, and correlation energies, we perform a successful calculation of the s -+ d interconfigurational energies (ICE's) for transition-metal atoms. The average error of the calculated ICE values for 3d atoms is only 0.2 eV. PACS number(s): 31.20.Sy, 31.20.Tz, 31.10.+z

The many-electron Schrödinger equation allows one to make predictions for the nonrelativistic ionization potentials of both highly charged positive atomic ions and neutral atoms in the limit of large atomic number Z. Beginning with theoretical configuration interaction data on both Li-and Be-like positive atomic ions by K.T. Chung et al. ͓Phys. Rev. A 45, 7766 ͑1992͒; Phys. Rev. A 47, 1740 ͑1993͔͒, their nonrelativistic first ionization potentials I are plotted in the form of I / Z 2 versus 1 / Z. In these two sequences, it is then clear that lim Z→ϱ ͑I / Z 2 ͒ remains finite and that this limit is approached essentially linearly. Interpretation is afforded by means of the so-called 1 / Z expansion of atomic theory. The question of the behavior of the nonrelativistic ionization potentials for large Z is then addressed for neutral atoms. We perform density functional theory ͑DFT͒ calculations using the local density approximation with Dirac exchange and neglecting Coulomb correlation for the heavy actinides as well as for the rare gas and alkali atoms from Z =10 up to Z = 291. Our results suggest that there is a nonzero value for lim Z→ϱ I for both the noble gases and the alkalis, the second one implying that there is a lower bound of about 2.56 eV to the ionization potential of any nonrelativistic neutral atom. We also explore an alternative approach via the one-body potential V͑r͒ of DFT by calculating the eigenenergies of the highest occupied atomic orbital in neutral atoms. Finally, relativistic corrections needed to compare measured ionization potentials to the predictions from the Schrödinger equation are briefly considered.

We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking.

Two families of regioisomeric 1,4-benzodiazepines, 4-benzyl-3H-benzo[e][1,4]diazepin-5-ones and 4-benzoyl-4,5-dihydro-3H-benzo[e][1,4]diazepines, have been synthesized through a similar Ugi/ reduction cyclization sequence. Their conformation and stability depend on the position of the tautomeric imine/enamine equilibrium present in the diazepine nucleus, which in turn depends on the relative position of the carbonyl group adjacent to the nitrogen at the 4-position in the benzodiazepine system.Moreover, the electrophilic center on the imine tautomer is essential for the antitumor activity of some benzodiazepines as a DNA binding position. The mechanism of tautomerization in the presence or absence of the oxo group has been studied computationally using DFT methods (B3LYP/6-31G** level).