An antioxidant mechanism of tetrahydrocannabinol (THC) and cannabidiol (CBD) were compared with a simplified model of α-tocopherol, butylhydroxytoluene and hydroxytoluene in order to understand the antioxidant nature of THC and CBD molecules using DFT. The following electronic properties were evaluated: frontier orbitals nature, ionization potential, O-H bond dissociation energy (BDE OH ), stabilization energy, and spin density distribution. An important factor that shows an influence in the antioxidant property of THC is the electron abstraction at the phenol position. Our data indicate that the decrease of the HOMO values and the highest ionization potential values are related to phenol, ether, and alkyl moieties. On the other hand, BDE OH in molecules with the cyclohexenyl group at ortho position of phenol are formed from lower energies than the molecules with an ether group at the meta position. In the light of our results, the properties calculated here predict that THC has a sightly higher antioxidant potential than CBD.

Current-density-functional theory is used to calculate ionization energies of current-carrying atomic states. A recently proposed perturbative approximation to full current-density-functional theory is implemented and found to be numerically feasible. Different parametrizations for the current-dependence of the density functional are critically compared. Orbital currents in open-shell atoms turn out to produce a small shift in the ionization energies. We find that modern density functionals have reached an accuracy at which small currentrelated terms appearing in open-shell configurations are not negligible anymore, compared to the remaining difference to experiment.

The generator coordinate (GC) method is a variational approach to the quantum many-body problem in which interacting many-body wave functions are constructed as superpositions of (generally nonorthogonal) eigenstates of auxiliary Hamiltonians containing a deformation parameter. This paper presents a time-dependent extension of the GC method as a new approach to improve existing approximations of the exchange-correlation (XC) potential in time-dependent density-functional theory (TDDFT). The time-dependent GC method is shown to be a conceptually and computationally simple tool to build memory effects into any existing adiabatic XC potential. As an illustration, the method is applied to driven parametric oscillations of two interacting electrons in a harmonic potential (Hooke's atom). It is demonstrated that a proper choice of time-dependent generator coordinates in conjunction with the adiabatic local-density approximation reproduces the exact linear and nonlinear two-electron dynamics quite accurately, including features associated with double excitations that cannot be captured by TDDFT in the adiabatic approximation.

The interaction between CO2 and 1,2-diaminoethane was computed using pure and hybrid density functionals. The CAM-B3LYP and wB97X-D functionals using a triple-ζ basis set that includes diffuse and polarization functions are the best functionals for calculating the relative energies of the zwitterion intermediate compared to a coupled-cluster with a single, double and non-iterative triple excitation (CCSD(T)) approach extrapolated to a complete basis set limit. With the two functionals and the triple-ζ basis set, the zwitterion is 1.70 kcal mol(-1) less stable than the reactants, and close to 1.63 kcal mol(-1) computed using the CCSD(T) approach. The inclusion of vibrational and thermal corrections and of entropic effects increases the relative energy of the zwitterion to 14.7 kcal mol(-1). Bending of the CO2 geometry increases its acidity due to a 1.09 eV reduction in the LUMO energy. Calculation of the CO2 interaction energy with a set of amines revealed that the interaction energies show a high correlation with their basicities, with the stronger bases stabilizing the zwitterion. For the most basic amine computed (3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidine), the Gibbs free energy of the zwitterion is 15.8 kcal mol(-1) lower than the reactants. Therefore, for this highly basic amine, the zwitterion may have a longer lifetime, in contrast to 2-aminoethanol (MEA), where it is only a transient species.

Current-density-functional theory is used to perturbatively calculate single-particle energies of open-shell atoms prepared in a current-carrying state. We focus on the highest occupied such energy, because its negative is, in principle, the exact ionization energy. A variety of different density functionals and calculational schemes are compared with each other and experiment. When the atom is prepared in a current-carrying state, a current-dependent exchange-correlation functional is found to slightly lower the single-particle energy of the current-carrying orbital, as compared to a calculation using standard (current independent) density functionals for the same system. The current-dependent terms in the exchange-correlation functional thus provide additional stabilization of the current-carrying state.

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In this work, the efficiency of partially hydrophobized hyperbranched polyglycerols (HPG11 and HPG12) as cetyltrimethylammonium bromide (CTAB) carriers was evaluated to prevent surfactant losses by adsorption on reservoir rocks surface during enhanced oil recovery (EOR) processes. Interactions between surfactant and polymers were studied by conductivity, zeta potential, and particle size measurements showing that complexes were formed between the components. The ability of PG, HPG11, HPG12 and those complexes to reduce the interfacial tension (IFT) was verified and one of the complexes was able to reduce the IFT to values under 1.0 mN/m, suggesting the occurrence of a synergy between the components. Molecular dynamics simulations indicated the preferential sites of interaction between surfactants and HPGs. HPG11:CTAB and HPG12:CTAB complexes' ability to permeate an unconsolidated porous medium and deliver the surfactant at the water–oil interface, increasing oil production, was evaluated through transport and oil displacement tests, and the results showed that the HPG12:CTAB complex led to almost 90% of oil recovery.

The vibrational circular dichroism (VCD) spectrum of l-alanine amino acid in aqueous solution in ambient conditions has been studied. The emphasis has been placed on the inclusion of the thermal disorder of the solute-solvent hydrogen bonds that characterize the aqueous solution condition. A combined and sequential use of molecular mechanics and quantum mechanics was adopted. To calculate the average VCD spectrum, the DFT B3LYP/6-311++G(d,p) level of calculation was employed, over one-hundred configurations composed of the solute plus all water molecules making hydrogen bonds with the solute. Simplified considerations including only four explicit solvent molecules and the polarizable continuum model were also made for comparison. Considering the large number of vibration frequencies with only limited experimental results a direct comparison is presented, when possible, and in addition a statistical analysis of the calculated values was performed. The results are found to be in line with the experiment, leading to the conclusion that including thermal disorder may improve the agreement of the vibrational frequencies with experimental results, but the thermal effects may be of greater value in the calculations of the rotational strengths.