HAB79: A New Molecular Dataset for Benchmarking DFT and DFTB Electronic Couplings Against High-Level Ab-initio Calculations

A new molecular dataset called HAB79 is introduced to provide ab-initio reference values for electronic couplings (transfer integrals) and to benchmark density functional theory (DFT) and density functional tight-binding (DFTB) calculations. The HAB79 dataset is comprised of 79 planar heterocyclic polyaromatic hydrocarbon molecules frequently encountered in organic (opto)electronics, arranged to 921 structurally diverse dimer configurations. We show that CASSCF/NEVPT2 with a minimal active space provides a robust reference method that can be applied to the relatively large molecules of the dataset. Electronic couplings are largest for cofacial dimers, in particular sulfur-containing polyaromatic hydrocarbons, with values in excess of 0.5 eV, followed by parallel displaced cofacial dimers. V-shaped dimer motifs, often encountered in the herringbone layers of organic crystals, exhibit medium-sized couplings whereas T-shaped dimers have the lowest couplings. DFT values obtained from the projector operator-based diabatization (POD) method are initially benchmarked against the smaller databases HAB11 (HAB7-) and found to systematically improve when climbing Jacob's ladder, giving mean relative unsigned errors (MRUE) of 27.7% (26.3%) for the GGA functional BLYP, 20.7% (15.8%) for hybrid functional B3LYP and 5.2% (7.5%) for the long-range corrected hybrid functional omega-B97X. Cost effective POD in combination with a GGA functional (PBE) and very efficient DFTB calculations on the dimers of the HAB79 database give a good linear correlation with the CASSCF/NEVPT2 reference data, which, after scaling with a multiplicative constant, gives reasonably small MRUEs of 17.9% and 40.1%, respectively, bearing in mind that couplings in HAB79 vary over 4 orders of magnitude

Quantum localization and delocalization of charge carriers in organic semiconducting crystals

Charge carrier transport in organic semiconductors is at the heart of many revolutionary technologies ranging from organic transistors, light-emitting diodes, flexible displays and photovoltaic cells. Yet, the nature of charge carriers and their transport mechanism in these materials is still unclear. Here we show that by solving the time-dependent electronic Schrödinger equation coupled to nuclear motion for eight organic molecular crystals, the excess charge carrier forms a polaron delocalized over up to 10–20 molecules in the most conductive crystals. The polaron propagates through the crystal by diffusive jumps over several lattice spacings at a time during which it expands more than twice its size. Computed values for polaron size and charge mobility are in excellent agreement with experimental estimates and correlate very well with the recently proposed transient localization theor

Chalk-steel Interface testing for marine energy foundations

The Energy Technology Partnership (ETP) and Lloyd’s Register EMEA are gratefully acknowledged for the funding of this project. The authors would also like to acknowledge the support of the European Regional Development Fund (ERDF) SMART Centre at the University of Dundee that allowed purchase of the equipment used during this study. The views expressed are those of the authors alone, and do not necessarily represent the views of their respective companies or employing organizations.Peer reviewedPostprin

Ampicillin/Sulbactam versus Cefuroxime as antimicrobial prophylaxis for cesarean delivery: a randomized study

<p>Abstract</p> <p>Background</p> <p>The efficacy and safety of a single dose of ampicillin/sulbactam compared to a single dose of cefuroxime at cord clamp for prevention of post-cesarean infectious morbidity has not been assessed.</p> <p>Methods</p> <p>Women scheduled for cesarean delivery were randomized to receive a single dose of either 3 g of ampicillin-sulbactam or 1.5 g of cefuroxime intravenously, after umbilical cord clamping. An evaluation for development of postoperative infections and risk factor analysis was performed.</p> <p>Results</p> <p>One hundred and seventy-six patients (median age 28 yrs, IQR: 24-32) were enrolled in the study during the period July 2004 - July 2005. Eighty-five (48.3%) received cefuroxime prophylaxis and 91 (51.7%) ampicillin/sulbactam. Postoperative infection developed in 5 of 86 (5.9%) patients that received cefuroxime compared to 8 of 91 (8.8%) patients that received ampicillin/sulbactam (p = 0.6). In univariate analyses 6 or more vaginal examinations prior to the operation (p = 0.004), membrane rupture for more than 6 hours (p = 0.08) and blood loss greater than 500 ml (p = 0.018) were associated with developing a postoperative surgical site infection (SSI). In logistic regression having 6 or more vaginal examinations was the most significant risk factor for a postoperative SSI (OR 6.8, 95% CI: 1.4-33.4, p = 0.019). Regular prenatal follow-up was associated with a protective effect (OR 0.04, 95% CI: 0.005-0.36, p = 0.004).</p> <p>Conclusions</p> <p>Ampicillin/sulbactam was as safe and effective as cefuroxime when administered for the prevention of infections following cesarean delivery.</p> <p>Trial registration</p> <p>Clinicaltrials.gov identifier: NCT01138852</p

Flickering Polarons Extending over Ten Nanometres Mediate Charge Transport in High‐Mobility Organic Crystals

Progress in the design of high‐mobility organic semiconductors has been hampered by an incomplete fundamental understanding of the elusive charge carrier dynamics mediating electrical current in these materials. To address this problem, a novel fully atomistic non‐adiabatic molecular dynamics approach termed fragment orbital‐based surface hopping (FOB‐SH) that propagates the electron‐nuclear motion has been further improved and, for the first time, used to calculate the full 2D charge mobility tensor for the conductive planes of six structurally well characterized organic single crystals, in good agreement with available experimental data. The nature of the charge carrier in these materials is best described as a flickering polaron constantly changing shape and extensions under the influence of thermal disorder. Thermal intra‐band excitations from modestly delocalized band edge states (up to 5 nm or 10–20 molecules) to highly delocalized tail states (up to 10 nm or 40–60 molecules in the most conductive materials) give rise to short, ≈ 10 fs‐long bursts of the charge carrier wavefunction that drives the spatial displacement of the polaron, resulting in carrier diffusion and mobility. This study implies that key to the design of high‐mobility materials is a high density of strongly delocalized and thermally accessible tail states

From Atomic Orbitals to Nano-scale Charge Transport with Mixed Quantum/Classical Non-adiabatic Dynamics: Method, Implementation and Application

An efficient computational method to perform fully atomistic mixed quantum/classical non-adiabatic molecular dynamics in nano-scale organic semiconductors is reviewed and its numerical implementation presented in detail. The methodology is termed fragment orbital-based surface hopping (FOB-SH) and rests on a DFT-parametrized tight-binding representation of the Hamiltonian (updated on-the-fly along the molecular dynamics) as well as an efficient calculation of nuclear gradients to propagate the coupled electron–nuclear dynamics. Common algorithmic extensions to the original surface hopping algorithm, such as the adjustment of the velocities along the non-adiabatic vectors upon successful non-adiabatic transitions and a decoherence correction, allow FOB-SH to reach total energy conservation, detailed balance and internal consistency. Further improvements and optimizations applied to FOB-SH to deal with a high density of electronic states characterizing condensed phase systems are discussed. Trivial crossing detection and a removal of decoherence correction-induced spurious charge transfers are particularly important for accurate dynamics and the convergence of charge carrier mobility and wavefunction delocalization with increasing system size. The application of FOB-SH to the calculation of charge mobilities and transport mechanism across the 2D high-mobility planes of experimentally well-known molecular crystals is presented

Different HLA-DR expression in endometriotic and adenomyotic lesions: Correlation with transvaginal ultrasonography Wndings

Objective Human leukocyte antigen-DR (HLA-DR) has been implicated in eutopic and ectopic glandular epithelial cells in endometriosis. We investigated the expression of HLA-DR in endometriotic and adenomyotic tissues within the stromal and glandular cells. Moreover, we correlate the HLA-DR expression according the transvaginal ultrasonography Wndings. Methods We studied operative and pathologic reports of 113 women who underwent laparoscopic or laparotomy treatment of endometrioma or adenomyosis. Tissues from 51 women with endometrioma and 62 women with adenomyosis were retrospectively evaluated. The distribution and intensity of the HLA-DR immunostaining was assessed using electron microscopy. Pathologic Wnding of the uterine junction zone and the size of endometrioma were evaluated with the laparoscopic results and the ultrasound Wndings. Results In adenomyosis tissues, the percentage of HLADR cells expression was significantly higher in stromal cells (83.9%) compared to glandular cells (25.8%), (p &lt; 0.001). The number of HLA-DR-positive endometriotic glandular cells was significantly higher than the total glandular adenomyotic cells (p &lt; 0.005). HLA-DR-positive cells was significantly different between stromal (p &lt; 0.016) and glandular cells (p &lt; 0.044) in each side of endometrioma. Finally, HLA-DR-positive percentage cells were significantly more frequent in the secretory phase than the proliferative in stromal and glandular cells in both groups. Conclusion HLA-DR antigen expression in endometrium and adenomyotic tissues. However, HLA-DR expression is distributed preferentially in glandular epithelial cells in endometrioma and in the adenomyotic stroma. In both groups the HLA-DR expression was significantly higher in the secretory phase than the proliferative or glandular and stroma cells. Larger perspective studies are needed to establish the expression of HLA antigens in immune reactions which occur in adenomyosis and endometriosis. © Springer-Verlag 2010