Nanodiamond collective electron states and their localization

The collective states despite their importance are rarely used to describe the electron structure of dielectric materials. The nature of the unrelated to impurities unpaired spins found experimentally in the nanodiamond is still under discussion. We propose the explanation of their nature in terms of the collective electron states. Collective states are studied by solving a one-particle one-dimensional Schrödinger equation in the Kronig–Penney potential and by ab initio computations of ground state wavefunctions of diamondoids $C_{78}H_{64}$, $C_{123}H_{100}$ and $C_{211}H_{140}$ at the DFT R-B3LYP/6-31G(d,p) level of theory. Three distinct classes were found: collective bonding states resembling modulated particle in a box solutions; surface-localized non-bonding conductive Tamm states and subsurface-localized bonding states for non-uniformly compressed nanodiamond. The existence of the unpaired spins is supposed to result from the spin-density fluctuation effects significant on the nanoscale collective and spread subsurface states.