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The oxygen evolution reaction (OER) is critical to solar production of fuels, but the reaction mechanism underlying the performance for a best OER catalyst, Fe-doped NiOOH [(Ni,Fe)OOH], remains highly controversial. We used grand canonical quantum mechanics to predict the OER mechanisms including kinetics and thus overpotentials as a function of Fe content in (Ni,Fe)OOH catalysts. We find that density functional theory (DFT) without exact exchange predicts that addition of Fe does not reduce the overpotential much. However, DFT with exact exchange predicts dramatic improvement in performance for (Ni,Fe)OOH, leading to an overpotential of 0.42 V and a Tafel slope of 23 mV/decade (dec), in good agreement with experiments, 0.3–0.4 V and 30 mV/dec. We reveal that the high spin d⁴ Fe(IV) leads to efficient formation of an active O radical intermediate, while the closed shell d⁶ Ni(IV) catalyzes the subsequent O–O coupling, and thus it is the synergy between Fe and Ni that delivers the optimal performance for OER.

The selection of a “perfect tool” for the theoretical determination of acid-base dissociation constants (Ka) is still puzzling. Recently, we developed a user-friendly model exploiting CAM-B3LYP for determining pKa with impressive reliability. Herein, a new challenge is faced, examining a panel of functionals belonging to different rungs of the “Jacob’s ladder” organization, which classifies functionals according to their level of theory. Specifically, meta-generalized gradient approximations (GGAs), hybrid-GGAs, and the more complex range-separated hybrid (RSH)-GGAs were investigated in predicting the pKa of differently substituted carboxylic acids. Therefore, CAM-B3LYP, WB97XD, B3PW91, PBE1PBE, PBEPBE and TPSSTPSS were used, with 6-311G+(d,p) as the basis set and the solvation model based on density (SMD). CAM-B3LYP showed the lowest mean absolute error value (MAE = 0.23) with relatively high processing time. PBE1PBE and B3PW91 provided satisfactory predictions (MAE = 0.34 and 0.38, respectively) with moderate computational time cost, while PBEPBE, TPSSTPSS and WB97XD led to unreliable results (MAE > 1). These findings validate the reliability of our model in predicting carboxylic acids pKa, with MAE well below 0.5 units, using a simplistic theoretical level and a low-cost computational approach.

This work explores the dispersed heterojunction of tris-(8-hydroxyquinoline) aluminum (AlQ3) and 8-hydroxyquinoline zinc (ZnQ2) with tetracyanoquinodimethane (TCNQ) and 2,6-diaminoanthraquinone (DAAq). Thin films of these organic semiconductors were deposited and analyzed, with their structures calculated with the B3PW91/6-31G** method. The optimized structure for AlQ3-TCNQ, AlQ3-DAAq, is achieved by means of three hydrogen bonds, whereas for ZnQ2-DAAq, two hydrogen interactions are predicted. These structures were recalculated including the GD3 dispersion term. A stable ordering was also achieved for AlQ3-TCNQ-GD3, AlQ3-DAAq-GD3, and ZnQ2-DAAq-GD3 with four and two hydrogen contacts for the former and the two latter, respectively. Infrared (IR) and UV-visible spectroscopy confirmed these theoretical predictions, in addition to obtaining the optical band gap for the films. The optical band gap values ranged between 1.62 and 2.97 eV (theoretical) and between 2.46 and 2.87 eV (experimental). Additional optical parameters and electrical behavior were obtained, which indicates the potential of the films to be used as organic semiconductors. All three films showed transmittance above 76%, which also broadens the range of applications in electrodes, transparent transistors, or photovoltaic cells. Devices fabricated using these materials displayed ohmic electrical behavior, with peak current values between 2 × 10−3 and 6 × 10−3 A.

SAMPL challenges (Mobley et al. in J Comput Aided Mol Des 28:135–150, 2014 ; Skillman in J Comput Aided Mol Des 26:473–474, 2012 ; Geballe in J Comput Aided Mol Des 24:259–279, 2010 ; Guthrie in J Phys Chem B 113:4501–4507, 2009 ) provide excellent opportunities to assess theoretical approaches on new data sets with a goal of gaining greater insight towards protein and ligand modeling. In the SAMPL5 experiment, cyclohexane–water partition coefficients were determined using a vertical solvation scheme in conjunction with the SMD continuum solvent model. Several DFT functionals partnered with correlation consistent basis sets were evaluated for the prediction of the partition coefficients. The approach chosen for the competition, a B3PW91 vertical solvation scheme, yields a mean absolute deviation of 1.9 logP units and performs well at estimating the correct hydrophilicity and hydrophobicity for the full SAMPL5 molecule set.

Ferulic acid (FA) and its derivatives (FADs) are known for a variety of biological activities, such as photo-protective agent, antioxidant, antiatherogenic and antiplasmodial activities. During structural definition of a FAD isolated from Croton pullei, the possibility of a heterologous series made this definition difficult. In this regard, computational simulations were performed using theoretical calculations at DFT level to predict Infrared (IR) and Nuclear Magnetic Resonance (NMR) data. The IR and NMR 13C and 1H data were compared with the theoretical calculations performed for three structural possibilities of a heterologous series. The theoretical results were compared with the experimental data through linear regression in order to define the most probable structure and showed satisfactory values.