21 research outputs found
Understanding the apparent fractional charge of protons in the aqueous electrochemical double layer
A detailed atomic-scale description of the electrochemical interface is essential to the understanding of electrochemical energy transformations. In this work, we investigate the charge of solvated protons at the Pt(111) | H_2O and Al(111) | H_2O interfaces. Using semi-local density-functional theory as well as hybrid functionals and embedded correlated wavefunction methods as higher-level benchmarks, we show that the effective charge of a solvated proton in the electrochemical double layer or outer Helmholtz plane at all levels of theory is fractional, when the solvated proton and solvent band edges are aligned correctly with the Fermi level of the metal (E_F). The observed fractional charge in the absence of frontier band misalignment arises from a significant overlap between the proton and the electron density from the metal surface, and results in an energetic difference between protons in bulk solution and those in the outer Helmholtz plane
Understanding the apparent fractional charge of protons in the aqueous electrochemical double layer
A detailed atomic-scale description of the electrochemical interface is essential to the understanding of electrochemical energy transformations. In this work, we investigate the charge of solvated protons at the Pt(111) | H_2O and Al(111) | H_2O interfaces. Using semi-local density-functional theory as well as hybrid functionals and embedded correlated wavefunction methods as higher-level benchmarks, we show that the effective charge of a solvated proton in the electrochemical double layer or outer Helmholtz plane at all levels of theory is fractional, when the solvated proton and solvent band edges are aligned correctly with the Fermi level of the metal (E_F). The observed fractional charge in the absence of frontier band misalignment arises from a significant overlap between the proton and the electron density from the metal surface, and results in an energetic difference between protons in bulk solution and those in the outer Helmholtz plane
A large-scale genome-wide association study meta-analysis of cannabis use disorder
Summary Background Variation in liability to cannabis use disorder has a strong genetic component (estimated twin and family heritability about 50–70%) and is associated with negative outcomes, including increased risk of psychopathology. The aim of the study was to conduct a large genome-wide association study (GWAS) to identify novel genetic variants associated with cannabis use disorder. Methods To conduct this GWAS meta-analysis of cannabis use disorder and identify associations with genetic loci, we used samples from the Psychiatric Genomics Consortium Substance Use Disorders working group, iPSYCH, and deCODE (20 916 case samples, 363 116 control samples in total), contrasting cannabis use disorder cases with controls. To examine the genetic overlap between cannabis use disorder and 22 traits of interest (chosen because of previously published phenotypic correlations [eg, psychiatric disorders] or hypothesised associations [eg, chronotype] with cannabis use disorder), we used linkage disequilibrium score regression to calculate genetic correlations. Findings We identified two genome-wide significant loci: a novel chromosome 7 locus (FOXP2, lead single-nucleotide polymorphism [SNP] rs7783012; odds ratio [OR] 1·11, 95% CI 1·07–1·15, p=1·84 × 10−9) and the previously identified chromosome 8 locus (near CHRNA2 and EPHX2, lead SNP rs4732724; OR 0·89, 95% CI 0·86–0·93, p=6·46 × 10−9). Cannabis use disorder and cannabis use were genetically correlated (rg 0·50, p=1·50 × 10−21), but they showed significantly different genetic correlations with 12 of the 22 traits we tested, suggesting at least partially different genetic underpinnings of cannabis use and cannabis use disorder. Cannabis use disorder was positively genetically correlated with other psychopathology, including ADHD, major depression, and schizophrenia. Interpretation These findings support the theory that cannabis use disorder has shared genetic liability with other psychopathology, and there is a distinction between genetic liability to cannabis use and cannabis use disorder. Funding National Institute of Mental Health; National Institute on Alcohol Abuse and Alcoholism; National Institute on Drug Abuse; Center for Genomics and Personalized Medicine and the Centre for Integrative Sequencing; The European Commission, Horizon 2020; National Institute of Child Health and Human Development; Health Research Council of New Zealand; National Institute on Aging; Wellcome Trust Case Control Consortium; UK Research and Innovation Medical Research Council (UKRI MRC); The Brain & Behavior Research Foundation; National Institute on Deafness and Other Communication Disorders; Substance Abuse and Mental Health Services Administration (SAMHSA); National Institute of Biomedical Imaging and Bioengineering; National Health and Medical Research Council (NHMRC) Australia; Tobacco-Related Disease Research Program of the University of California; Families for Borderline Personality Disorder Research (Beth and Rob Elliott) 2018 NARSAD Young Investigator Grant; The National Child Health Research Foundation (Cure Kids); The Canterbury Medical Research Foundation; The New Zealand Lottery Grants Board; The University of Otago; The Carney Centre for Pharmacogenomics; The James Hume Bequest Fund; National Institutes of Health: Genes, Environment and Health Initiative; National Institutes of Health; National Cancer Institute; The William T Grant Foundation; Australian Research Council; The Virginia Tobacco Settlement Foundation; The VISN 1 and VISN 4 Mental Illness Research, Education, and Clinical Centers of the US Department of Veterans Affairs; The 5th Framework Programme (FP-5) GenomEUtwin Project; The Lundbeck Foundation; NIH-funded Shared Instrumentation Grant S10RR025141; Clinical Translational Sciences Award grants; National Institute of Neurological Disorders and Stroke; National Heart, Lung, and Blood Institute; National Institute of General Medical Sciences.Peer reviewe
Shared genetic risk between eating disorder- and substance-use-related phenotypes:Evidence from genome-wide association studies
First published: 16 February 202
Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package
This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design
Transancestral GWAS of alcohol dependence reveals common genetic underpinnings with psychiatric disorders
Liability to alcohol dependence (AD) is heritable, but little is known about its complex polygenic architecture or its genetic relationship with other disorders. To discover loci associated with AD and characterize the relationship between AD and other psychiatric and behavioral outcomes, we carried out the largest genome-wide association study to date of DSM-IV-diagnosed AD. Genome-wide data on 14,904 individuals with AD and 37,944 controls from 28 case-control and family-based studies were meta-analyzed, stratified by genetic ancestry (European, n = 46,568; African, n = 6,280). Independent, genome-wide significant effects of different ADH1B variants were identified in European (rs1229984; P = 9.8 x 10(-13)) and African ancestries (rs2066702; P = 2.2 x 10(-9)). Significant genetic correlations were observed with 17 phenotypes, including schizophrenia, attention deficit-hyperactivity disorder, depression, and use of cigarettes and cannabis. The genetic underpinnings of AD only partially overlap with those for alcohol consumption, underscoring the genetic distinction between pathological and nonpathological drinking behaviors.Peer reviewe
Nanoscale analysis of plastic contaminants migration in packaging materials and potential leaching into model food systems
Polymers are the most common packaging materials used for food, beverages, cosmetics, and other consumer products. The ever-growing concern over pollution generated from single-use packaging materials, and the ensuing potential environment contamination resulting from their use has raised safety questions. Polymers used in these materials are often not spared from the presence of impurities, including unreacted monomers and small oligomers. The characterization of transport properties, including diffusion and leaching of these penetrant molecules is largely hampered by the long timescales involved in shelf-life experiments. In this work, we employ molecular simulation techniques to explore the main mechanisms involved in the bulk and interfacial transport of monomer molecules from three polymers commonly employed as packaging materials: polyamide-6, polycarbonate, and poly(methyl-methacrylate). Our simulations shed light on the main diffusion mechanisms for in- and outbound penetrant diffusion and provide rationalization for monomer leaching in model food formulations as well as bulky industry-relevant molecules. With these molecular-scale characterization we provide base insights to aid the design of polymer/consumer product interfaces with reduced risk of contamination and longer shelf-life
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Ab Initio Kinetics of Hydrogen Abstraction from Methyl Acetate by Hydrogen, Methyl, Oxygen, Hydroxyl, and Hydroperoxy Radicals
The
kinetics of hydrogen abstraction by five radicals (H, O(<sup>3</sup><i>P</i>), OH, CH<sub>3</sub>, and HO<sub>2</sub>) from
methyl acetate (MA) is investigated theoretically in order
to gain further understanding of certain aspects of the combustion
chemistry of biodiesels, such as the effect of the ester moiety. We
employ ab initio quantum chemistry methods, coupled cluster singles
and doubles with perturbative triples correction (CCSD(T)) and multireference
averaged coupled pair functional theory (MRACPF2), to predict chemically
accurate reaction energetics. Overall, MRACPF2 predicts slightly higher
barrier heights than CCSD(T) for MA + H/CH<sub>3</sub>/O/OH, but slightly
lower barrier heights for hydrogen abstraction by HO<sub>2</sub>.
Based on the obtained reaction energies, we also report high-pressure-limit
rate constants using transition state theory (TST) in conjunction
with the separable-hindered-rotor approximation, the variable reaction
coordinate TST, and the multi-structure all-structure approach. The
fitted modified Arrhenius expressions are provided over a temperature
range of 250 to 2000 K. The predictions are in good agreement with
available experimental results. Abstractions from both of the methyl
groups in MA are expected to contribute to consumption of the fuel
as they exhibit similar rate coefficients. The reactions involving
the OH radical are predicted to have the highest rates among the five
abstracting radicals, while those initiated by HO<sub>2</sub> are
expected to be the lowest
Density Fitting and Cholesky Decomposition of the Two-Electron Integrals in Local Multireference Configuration Interaction Theory
To
treat large molecules with accurate ab initio quantum chemistry,
reduced scaling correlated wave function methods are now commonly
employed. Optimization of these wave functions in practice requires
some approximation of the two-electron integrals. Both Cholesky decomposition
(CD) and density fitting (DF) are widely used approaches to approximate
these integrals. Here, we compare CD and DF for use in local multireference
singles and doubles configuration interaction (LMRSDCI). DF-LMRSDCI
provides less accurate total energies than CD-LMRSDCI, but both methods
are accurate for energy differences. However, DF-LMRSDCI is significantly
less computationally expensive than CD-LMRSDCI on the molecules tested,
suggesting that DF-LMRSDCI is an efficient, often sufficiently accurate
alternative to our previously reported CD-LMRSDCI method
Identification of Plasmons in Molecules with Scaled Ab Initio Approaches
For
the electronic excitations in metallic systems under periodic
boundary conditions, momentum conservation and a uniform electron–electron
interaction imply a clear distinction of plasmons and single-particle
excitations. For finite molecular systems, this distinction is less
clear, but excitations formed by a coherent superposition of elementary
particle–hole transitions that show a collective oscillation
of the transition electron density have nevertheless been identified
as plasmons in molecules. To aid this distinction, a scaling approach
[Bernadotte, S.; Evers, F.; Jacob, C. R. <i>J. Phys. Chem. C</i> <b>2013</b>, <i>117</i>, 1863] has recently been
developed that is based on the observation that, in contrast to single-particle
excitations, plasmonic excitation energies strongly depend on the
electron–electron interaction. In this work, we adapt the proposed
scaling scheme to ab initio models, specifically configuration interaction
singles and the second-order algebraic diagrammatic construction scheme
of the polarization propagator. The resulting approach is applied
to a series of linear polyenes and the characterization based on the
scaling method is confirmed by inspection of the eigenvector components,
transition density patterns, and transition strengths