NENCI-2021. I. A large benchmark database of non-equilibrium non-covalent interactions emphasizing close intermolecular contacts.

In this work, we present NENCI-2021, a benchmark database of ∼8000 Non-Equilibirum Non-Covalent Interaction energies for a large and diverse selection of intermolecular complexes of biological and chemical relevance. To meet the growing demand for large and high-quality quantum mechanical data in the chemical sciences, NENCI-2021 starts with the 101 molecular dimers in the widely used S66 and S101 databases and extends the scope of these works by (i) including 40 cation-π and anion-π complexes, a fundamentally important class of non-covalent interactions that are found throughout nature and pose a substantial challenge to theory, and (ii) systematically sampling all 141 intermolecular potential energy surfaces (PESs) by simultaneously varying the intermolecular distance and intermolecular angle in each dimer. Designed with an emphasis on close contacts, the complexes in NENCI-2021 were generated by sampling seven intermolecular distances along each PES (ranging from 0.7× to 1.1× the equilibrium separation) and nine intermolecular angles per distance (five for each ion-π complex), yielding an extensive database of 7763 benchmark intermolecular interaction energies (Eint) obtained at the coupled-cluster with singles, doubles, and perturbative triples/complete basis set [CCSD(T)/CBS] level of theory. The Eint values in NENCI-2021 span a total of 225.3 kcal/mol, ranging from -38.5 to +186.8 kcal/mol, with a mean (median) Eint value of -1.06 kcal/mol (-2.39 kcal/mol). In addition, a wide range of intermolecular atom-pair distances are also present in NENCI-2021, where close intermolecular contacts involving atoms that are located within the so-called van der Waals envelope are prevalent-these interactions, in particular, pose an enormous challenge for molecular modeling and are observed in many important chemical and biological systems. A detailed symmetry-adapted perturbation theory (SAPT)-based energy decomposition analysis also confirms the diverse and comprehensive nature of the intermolecular binding motifs present in NENCI-2021, which now includes a significant number of primarily induction-bound dimers (e.g., cation-π complexes). NENCI-2021 thus spans all regions of the SAPT ternary diagram, thereby warranting a new four-category classification scheme that includes complexes primarily bound by electrostatics (3499), induction (700), dispersion (1372), or mixtures thereof (2192). A critical error analysis performed on a representative set of intermolecular complexes in NENCI-2021 demonstrates that the Eint values provided herein have an average error of ±0.1 kcal/mol, even for complexes with strongly repulsive Eint values, and maximum errors of ±0.2-0.3 kcal/mol (i.e., ∼±1.0 kJ/mol) for the most challenging cases. For these reasons, we expect that NENCI-2021 will play an important role in the testing, training, and development of next-generation classical and polarizable force fields, density functional theory approximations, wavefunction theory methods, and machine learning based intra- and inter-molecular potentials.

Designing an All-Solid-State Sodium-Carbon Dioxide Battery Enabled by Nitrogen-Doped Nanocarbon.

All-solid-state sodium-carbon dioxide (Na-CO2) battery is an emerging technology that effectively utilizes the greenhouse gas, CO2, for energy storage with the virtues of minimized electrolyte leakage and suppressed Na dendrite growth for the Na metal anode. However, the sluggish reduction/evolution reactions of CO2 on the solid electrolyte/CO2 cathode interface have caused premature battery failure. Herein, nitrogen (N)-doped nanocarbon derived from metal-organic frameworks is designed as a cathode catalyst to solve this challenge. The porous and highly conductive N-doped nanocarbon possesses superior uptake and binding capability with CO2, which significantly accelerates the CO2 electroreduction and promotes the formation of thin sheetlike discharged products (200 nm in thickness) that can be easily decomposed upon charging. Accordingly, reduced discharge/charge overpotential, high discharge capacity (>10 000 mAh g-1), long cycle life, and high energy density (180 Wh kg-1 in pouch cells) are achieved at 50 °C.

Size effects and odd-even effects in MoS2 nanosheets: first-principles studies.

Molybdenum disulfide (MoS2) nanostructures have been widely used as catalysts in the petroleum refinery industry for the hydrodesulfurization process, in which sulfur vacancies play a critical role in determining the catalytic activity. Here we report size effects and odd-even effects on the formation of sulfur vacancies in the triangular MoS2 nanosheets using first-principles calculations. By modeling four types of edge structures of MoS2 nanosheets, S-terminated edges are found to be energetically more favorable than Mo-terminated edges, and are then selected for studying energetics of sulfur vacancies. Two types of sulfur dimer vacancies at the center (VS@Cen) and at the corner (VS@Cnr) of the edges of S-terminated MoS2 nanosheets are modeled, respectively. Our results reveal a strong odd-even effect on the formation of sulfur dimer vacancies, particularly for small MoS2 nanosheets, in terms of the size of nanosheets that is defined by the number of Mo atoms on the edge. The VS@Cen dimer vacancy has a low formation energy at an even-number but a high formation energy at an odd-number, while the VS@Cnr dimer vacancy exhibits a complete opposite trend. These results indicate that small MoS2 nanosheets can exhibit unique material properties for catalytic applications.

Energetic stability, oxidation states, and electronic structure of Bi-doped NaTaO3: a first-principles hybrid functional study.

We studied the defect formation energies, oxidation states of the dopants, and electronic structures of Bi-doped NaTaO3 using first-principles hybrid density functional theory calculations. Three possible structural models, including Bi-doped NaTaO3 with Bi at the Na site (Bi@Na), with Bi at the Ta site (Bi@Ta), and with Bi at both Na and Ta sites [Bi@(Na,Ta)], are constructed. Our results show that the preferred doping sites of Bi are strongly related to the preparation conditions of NaTaO3. It is energetically more favorable to form a Bi@Na structure under Na-poor conditions, to form a Bi@Ta structure under Na-rich conditions, and to form a Bi@(Na,Ta) structure under mildly Na-rich conditions. The Bi@Na doped model shows an n-type conducting character along with an expected blueshift of the optical absorption edge, in which the Bi atoms exist as Bi(3+) (6s(2)6p(0)). The Bi@Ta doped model has empty gap states consisting of Bi 6s states in its band gap, which can lead to visible-light absorption via the electron transition among the valence band, the conduction band, and the gap states. The Bi dopant is present as a Bi(5+) ion in this model, consistent with the experimental results. In contrast, the Bi@(Na,Ta) doped model has occupied gap states consisting of Bi 6s states in its band gap, and thus visible-light absorption is also expected in this system due to electron excitation from these occupied states to the conduction band, in which the Bi dopants exist as Bi(3+) ions. Our first-principles electronic structure calculations revealed the relationship between the Bi doping sites and the material preparation conditions, and clarified the oxidation states of Bi dopants in NaTaO3 as well as the origin of different visible-light photocatalytic hydrogen evolution behaviors in Bi@Ta and Bi@(Na,Ta) doped NaTaO3. This work can provide a useful reference for preparing a Bi-doped NaTaO3 photocatalyst with desired doping sites.

Unexpected Intraoperative Findings, Situations, and Complications in Bariatric Surgery.

BACKGROUND: Bariatric surgery is considered a safe therapy to treat obesity. Postoperative complications are well known; however, there is a lack of data describing intraoperative complications and/or unexpected findings, and if there is further impact on outcomes. METHODS: Retrospective study with patients operated between 2013 and 2016 at a single institution. All operative information was collected prospectively and aimed to analyze the incidence and causes of unexpected intraoperative findings, complications, change in surgical plan, extra surgeries, and procedure interruption in patients submitted to bariatric surgery. Secondarily, a morbidity analysis was performed, correlating intraoperative complications with postoperative complications and length of stay. RESULTS: Four-hundred and five patients were included. Female sex comprised 82% of cases, and a median age of 38 years old was observed; almost 90% were gastric bypass. In 29.3% of cases, there were intraoperative findings, mainly adhesions, abdominal wall hernias, positive methylene blue test, hiatal hernias, and gastrointestinal stromal tumors. Associated surgeries were performed in 8.6% cases, and intraoperative adverse events reported in 7.1%, where organ injury and anastomosis problems were the most frequent. A change in the operative plan was done in 0.9% and surgery interruption in 1.2% of the cases. Early complications were observed in 6.6%. There was no correlation between intraoperative complications and length of stay or early complications. CONCLUSION: Unexpected intraoperative findings/complications are common in bariatric surgery, but without increasing morbidity or length of stay. Surgery suspension, change in the planned technique, or adding extra (non-bariatric) procedures may occur.

Metabolic syndrome 2 years after laparoscopic gastric bypass.

BACKGROUND: The latest diabetes consensus identified obesity as key component of the metabolic syndrome. The role of bariatric surgery over such syndrome has been less explored with a lack of long term studies, and especially among Mexicans. METHODS: Retrospective study including patients with metabolic syndrome submitted to laparoscopic gastric bypass at a single institution with complete data after 24 months. The objective was to analyze the improvement of the syndrome and each component. Demographic, anthropometric, biochemical and clinical parameters were analyzed at 12 and 24 months. Secondarily weight loss and other parameters were also analyzed. Finally, an analysis of syndrome improvement related to weight loss was performed. RESULTS: Sixty-three patients were included. The 2 most common components associated with obesity were reduced HDL and raised glucose or Type 2 diabetes. There was a significant improvement of metabolic syndrome and its components, as well as for the rest of the analyzed data, from the first check point and throughout follow-up. Prevalence of such syndrome was 6.3% at 12 and 24 months. Hypertension and raised glucose or Type 2 diabetes were the components with the greatest and fastest improvement; HDL levels and obesity were the least improved. There was a direct relationship between percentage of excess weight loss or percentage of excess BMI loss, and syndrome's improvement. CONCLUSION: Patients with metabolic syndrome improved after gastric bypass, with results lasting after 2 years; other metabolic parameters important for cardiovascular risk were also positively affected. There was a relationship between the amount of weight loss and improvement of metabolic syndrome.