Chemical Bond Structure of Metal-Incorporated Carbon System

The interactions between incorporated metal atoms (Me) and carbon atom were investigated by the first-principles calculations based on the density functional theory. The simplified tetrahedral cluster model was used. The electronic structure analysis revealed that the ionic bond was generated between I A∼III A metal atom (Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Al, Ga, In, Tl) and C atoms except Be case; for all transition metals, the characteristic of highest occupied molecular orbital changed from bonding (Sc, Y, Lu, Ti, Zr, Hf) to nonbonding (V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os) and to antibonding (Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg) as d electrons increased. The different bond characteristics and the partial ionic contribution caused by the electronegative difference between Me and C atoms reduced the strength and directionality of bond which explained the smaller energy changes of Me–(CH3� 4 systems to the external distortion of the structure. These results also implied that the compressive stress in carbon-based systems could be reduced by the incorporation of these metals.