Transition metal embedded g-C3N4 sheets demonstrate promising multi usage in various fields such as memory devices, photocatalysis.

The lack of intrinsic spin polarization in graphene as well as in its several composites limits their usage as suitable spintronic material. Using long-range dispersion corrected density functional theory, we explore the structural, electronic, magnetic, and optical properties of recently synthesized [Liu, Q.; Zhang, J. Langmuir 2013, 29, 3821−3828] two-dimensional graphitic carbon nitride (g-C 3 N 4 ) stacked graphene (C 3 N 4 @graphene) where 3d transition metals (TMs) are embedded in the cavity of g-C 3 N 4 (TM-C 3 N 4 @ graphene). The incorporation of TMs modifies the structure of C 3 N 4 @graphene negligibly and keeps graphene almost as in its pristine form. TM inclusion makes the narrow-gap semiconducting C 3 N 4 @graphene as metallic. Charge-transfer analysis shows that the TM-C 3 N 4 transfers electrons from the 3d-orbital of TM to the conduction band of graphene, making it n-doped in nature. Importantly, Cr, Fe, Co, and Ni embedded C 3 N 4 @graphene shows long-range ferromagnetic coupling among TMs in their ground state. The magnetic ordering appears due to suitable ferromagnetic d−p exchange interaction, which is absent in paramagnetic V-and Mn-C 3 N 4 @graphene sheets. Furthermore, calculated high charge carrier densities of the n-doped graphene layer in these nanocomposites are quite promising for its usage in ultrafast electronics. Performing Heisenberg model based Monte Carlo simulations, we predict the Curie temperatures for Crand Fe-C 3 N 4 @graphene as 381 and 428 K, respectively. Moreover, these sheets also demonstrate prominent visible light response, which gives us a clue about their probable photocatalytic activity. Thus, the present study exhibits the true multifunctional behavior of TM-C 3 N 4 @graphene by demonstrating its usage in various fields, such as memory devices, spintronics, ultrafast electronics, photocatalysis, etc.

We have studied the topological and local aromaticity of BN-substituted benzene, pyrene, chrysene, triphenylene and tetracene molecules. The nucleus-independent chemical shielding (NICS), harmonic oscillator model of aromaticity (HOMA), para-delocalization index (PDI) and aromatic fluctuation index (FLU) have been calculated to quantify aromaticity in terms of magnetic and structural criteria. We find that charge separations due to the introduction of heteroatoms largely affect both the local and topological aromaticity of these molecules. Our studies show that the presence of any kind of heteroatom in the ring not only reduces the local delocalization in the six membered ring, but also affects strongly the topological aromaticity. In fact, the relative orders of the topological and local aromaticity depend strongly on the position of the heteroatoms in the structure. In general, more ring shared BN containing molecules are less aromatic than the less ring shared BN molecules. In addition our results provide evidence that the structural stability of the molecule is dominated by the σ bond rather than the π bond.

Many metallabenzene complexes appear to exhibit an enhanced thermodynamic stability which has been attributed to the concept of aromaticity. Analysis of the ring currents induced by a magnetic field, either by direct visualization or by considering nuclear or nucleus-independent chemical shielding values (NMR or NICS), have become useful theoretical tools to characterize the aromaticity of many molecules involving the main group elements. We have analyzed 21 metallabenzenes using variations of these techniques, which take account of the large core and metal orbital contributions which often lead to transition-metal-containing systems exhibiting anomalous shielding values. Analysis of individual orbital contributions to both the ring currents and chemical shielding values based upon the ipsocentric and CSGT (continuous set of gauge transformations) methods has shown that complexes such as the 18 electron Ir or Rh(C 5H 5)(PH 3) 2Cl 2 molecules should be classed as aromatic, whereas the 16 electron complexes such as Os or Ru(C 5H 5)(PH 3) 2Cl 2 should not, despite having the same occupancy of pi-MOs. The differences can be directly attributed to the HOMO/LUMO b 2 in-plane (d xy ) molecular orbital, which, when unoccupied, is available to disrupt the delocalized currents typical of aromatic systems. A range of Pd and Pt metallabenzenes with cyclopentadienyl and phosphine ligands is also discussed as having aromatic and nonaromatic character, respectively.

Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations have been employed to investigate the possibility of 2D boron sheets (BSs) as an anode material in lithium ion batteries (LIBs).Among a, a 1 and h 4/28 metallic BSs, planarity is retained for the a 1 and h 4/28 polymorphs after the formation of the layered structure. The optimum anodic nature of the a 1 and a 1 -AA polymorphs has been suggested based on their electronic, structural and Li adsorption/desorption studies. The highly symmetric 'H' site is energetically favored for Li adsorption at both 0 and 298 K. Li migration occurs from one 'H' site to another via the top of a boron atom, with a 0.66 and 0.39 eV energy barrier at 0 and 298 K respectively. An increase in the lithium concentration, up to a 50% coverage of 'H' sites, decreases the diffusion barrier gradually and reaches the saturation point at 0.59 eV (at 0 K). The lithium saturation requires eight lithium atoms per 1.63 nm 2 surface area of the a 1 sheet, when all 'H' sites become occupied. This confers the theoretical estimate of the capacity as 383 mA h g À1 , which is higher than that of the conventional graphitic electrode. Finally, the structural stability at the lithium saturation point is confirmed by increasing the number of layers up to four. All of these characteristics suggest the appropriateness of a 1 -AA as an anode material for LIBs.