We have investigated intermolecular charge transfer (CT) excited states and demonstrated their contribution to the excitation-relaxation and photocarrier generation mechanisms for both ${\mathrm{C}}_{60}$ and ${\mathrm{C}}_{70}$ polycrystalline films. This has been done (1) experimentally, using UV-visible absorption (Abs) and electroabsorption (EA), luminescence and its modulation by external electric-field and steady-state photoconductivity; (2) semiempirically, analyzing the Abs and EA spectra in order to determine the CT state energies and to estimate the variation of the average polarizability tensor and the dipole moment; and (3) theoretically, by performing calculations of polarization energies and electrostatic stabilization energies. The most significant CT states have been identified at approximately 2.43 and 3.50 eV for ${\mathrm{C}}_{60}$ films and at 2.26 and 3.60 eV for ${\mathrm{C}}_{70}$ films (data from the semiempirical analysis). Their properties have been discussed in terms of crystallographic and electronic structure, with special emphasis on their mixing with Frenkel states.

Electronic structures of ${\mathrm{C}}_{\mathrm{60}}$ and its endohedral complexes with Li, Na, K, Be, Mg, Ca, La, B, and Al have been calculated by means of density functional methodology. The electronic distributions have been analyzed from the point of view of the guest-host electron transfer. Alkali metals and Al have been found to donate their outermost electron to the fullerene cage. There is no electron transfer for Be, while for B, Mg, Ca, and La the transfer is only partial. For the entire series, ionization potentials and electron affinities have been calculated which are in excellent agreement with the few values known from experiments. The results are consistent with the donor-acceptor properties of the guest atom.

Although the electrical conductivity of an electrolyte can be estimated from the molecular dynamics trajectory, it is often a challenging task because of the need to obtain a substantial amount of data to ensure sufficient averaging. Here, we present an analysis on the convergence of results with the number of simulated trajectories. A series of molecular dynamics simulations have been performed for a model electrolyte (NaCl in water) and the Einstein relation has been used to calculate the electrical conductivity. The standard deviation of the conductivity estimates is relatively large compared to the mean value, and it has been shown that the off-diagonal contributions to the collective displacement of ions are responsible for large deviations between systems. It has been found that about 40 independent MD simulations may be required to reduce the errors. A procedure to improve the final estimate of the conductivity has been proposed.

Solvent-induced shifts in the absorption spectrum of N,N-diethyl-4-nitroaniline were studied by quantum-chemical methods in water, dimethylsulfoxide, acetonitrile and acetone. TDDFT methodology and semiempirical ZINDO/S and PM6-CIS approaches were used to calculate excitation energies. Solvent effect was modeled in implicit solvent model by different variants of the PCM approach. Classical molecular dynamics was applied to obtain solute–solvent geometries used in explicit solvent modeling. Most implicit solvent models fail to reproduce the sequence of solvatochromic shifts for four studied solvents, usually yielding too small effect for water. The best result of the PCM method was obtained with SMD atomic radii. Semiempirical quantum-chemical methods in explicit solvent model did not provide satisfactory description of solvatochromic shifts with the largest disagreement to experiment observed for water. TDDFT explicit solvent calculations performed the best in modeling of spectral shifts. Problems with reproduction of experimental data were attributed to specific interactions.