The Initial Relationship Between the United States Department of Health and Human Services' Digital COVID-19 Public Education Campaign and Vaccine Uptake: Campaign Effectiveness Evaluation.

BACKGROUND: Over 1 million people in the United States have died of COVID-19. In response to this public health crisis, the US Department of Health and Human Services launched the We Can Do This public education campaign in April 2021 to increase vaccine confidence. The campaign uses a mix of digital, television, print, radio, and out-of-home channels to reach target audiences. However, the impact of this campaign on vaccine uptake has not yet been assessed. OBJECTIVE: We aimed to address this gap by assessing the association between the We Can Do This COVID-19 public education campaign's digital impressions and the likelihood of first-dose COVID-19 vaccination among US adults. METHODS: A nationally representative sample of 3642 adults recruited from a US probability panel was surveyed over 3 waves (wave 1: January to February 2021; wave 2: May to June 2021; and wave 3: September to November 2021) regarding COVID-19 vaccination, vaccine confidence, and sociodemographics. Survey data were merged with weekly paid digital campaign impressions delivered to each respondent's media market (designated market area [DMA]) during that period. The unit of analysis was the survey respondent-broadcast week, with respondents nested by DMA. Data were analyzed using a multilevel logit model with varying intercepts by DMA and time-fixed effects. RESULTS: The We Can Do This digital campaign was successful in encouraging first-dose COVID-19 vaccination. The findings were robust to multiple modeling specifications, with the independent effect of the change in the campaign's digital dose remaining practically unchanged across all models. Increases in DMA-level paid digital campaign impressions in a given week from -30,000 to 30,000 increased the likelihood of first-dose COVID-19 vaccination by 125%. CONCLUSIONS: Results from this study provide initial evidence of the We Can Do This campaign's digital impact on vaccine uptake. The size and length of the Department of Health and Human Services We Can Do This public education campaign make it uniquely situated to examine the impact of a digital campaign on COVID-19 vaccination, which may help inform future vaccine communication efforts and broader public education efforts. These findings suggest that campaign digital dose is positively associated with COVID-19 vaccination uptake among US adults; future research assessing campaign impact on reduced COVID-19-attributed morbidity and mortality and other benefits is recommended. This study indicates that digital channels have played an important role in the COVID-19 pandemic response. Digital outreach may be integral in addressing future pandemics and could even play a role in addressing nonpandemic public health crises.

How Are We Doing? A Scoping Review of Published Patient-Centered Outcomes Research in United States Student-Run Free Clinics.

Phenomenon: Student-run free clinics (SRFCs) serve an integral role in most United States (US) medical schools and contribute substantially to literature on the quality of care to uninsured persons. There has been substantial growth over the past decade of scholarly work produced by SRFCs as they have increased in size and number. Research on patient care outcomes informs better care structures for patients, however there is no current synthesis of patient care outcomes research among SRFCs. This article provides an overview of SRFC research on patient outcomes to understand current research domains and to identify gaps in the literature. Approach: We completed a scoping review by searching Scopus, PubMed, and Journal of Student Run Clinics in June 2021. All peer-reviewed, English-language articles focused on patient-centered outcomes at SRFCs in the US were included. Two independent reviewers performed title, abstract, and full-text screening of relevant works, and eight reviewers conducted data extraction. Descriptive data analysis was performed along with relevant content analysis of patient-centered outcomes. Findings: The search strategy identified 784 studies, of which 87 met inclusion criteria. Most studies were published within the last six years (81.6%), located in California, New York, or Florida (43.7%), and intervention based (33.3%). Many studies (46.0%) had a specific disease of focus of which diabetes was the most researched(19.5%). Patient-centered studies were the leading focus of the study aims (40.2%), where key findings demonstrated primarily improved outcomes in clinic metrics post-intervention (36.8%) or equivalent/better clinical performance than national metrics (20.7%). Insights: This review brings to light gaps in the literature reporting research in SRFCs and can be applied to other low-resource settings. Future efforts to expand SRFC outcomes research should focus on community relationship building, understanding institutional support, and ensuring education on best practices for research within SRFCs. Doing so informs patient care improvement as SRFCs continue to operate as safety net clinics for marginalized populations.

Insertion of the Liquid Crystal 5CB into Monovacancy Graphene.

Interfacial interactions between liquid crystal (LC) and two-dimensional (2D) materials provide a platform to facilitate novel optical and electronic material properties. These interactions are uniquely sensitive to the local energy landscape of the atomically thick 2D surface, which can be strongly influenced by defects that are introduced, either by design or as a byproduct of fabrication processes. Herein, we present density functional theory (DFT) calculations of the LC mesogen 4-cyan-4'-pentylbiphenyl (5CB) on graphene in the presence of a monovacancy (MV-G). We find that the monovacancy strengthens the binding of 5CB in the planar alignment and that the structure is lower in energy than the corresponding homeotropic structure. However, if the molecule is able to approach the monovacancy homeotropically, 5CB undergoes a chemical reaction, releasing 4.5 eV in the process. This reaction follows a step-by-step process gradually adding bonds, inserting the 5CB cyano group into MV-G. We conclude that this irreversible insertion reaction is likely spontaneous, potentially providing a new avenue for controlling both LC behavior and graphene properties.

Dutasteride Improves Nocturia but Does Not Lead to Better Sleep: Results from the REDUCE Clinical Trial.

PURPOSE: In men, complaints of nocturia causing poor sleep are often attributed to benign prostatic hyperplasia and treated with benign prostatic hyperplasia medications. We assessed whether treating lower urinary tract symptoms with dutasteride altered either nocturia or sleep quality using data from REDUCE. MATERIALS AND METHODS: REDUCE was a 4-year randomized, multicenter trial comparing dutasteride 0.5 mg/day vs placebo for prostate cancer chemoprevention. Study participants were men considered at increased risk for prostate cancer. Eligibility included age 50-75 years, prostate specific antigen 2.5-10 ng/ml, and 1 negative prostate biopsy. At baseline, 2 years and 4 years, men completed the International Prostate Symptom Score and Medical Outcomes Study Sleep Scale, a 6-item scale assessing sleep. To test differences in nocturia and Medical Outcomes Study Sleep Scale over time, we used linear mixed models adjusted for baseline confounders. Subanalyses were conducted in men symptomatic from lower urinary tract symptoms, nocturia, poor sleep, or combinations thereof. RESULTS: Of 6,914 men with complete baseline data, 80% and 59% were assessed at 2 and 4-year followup, respectively. Baseline characteristics were balanced between treatment arms. Dutasteride improved nocturia at 2 (-0.15, 95% CI -0.21, -0.09) and 4 years (-0.24, 95% CI -0.31, -0.18) but did not improve sleep. When limited to men symptomatic from lower urinary tract symptoms, nocturia, poor sleep or combinations thereof, results mirrored findings from the full cohort. CONCLUSIONS: In men with poor sleep who complain of nocturia, treatment of lower urinary tract symptoms with dutasteride modestly improves nocturia but has no effect on sleep. These results suggest men with poor sleep who complain of nocturia may not benefit from oral benign prostatic hyperplasia treatment.

Synthesis and Structure of Sn14Cl6(CH2SiMe3)12: Toward Nanoclusters of 4-Coordinate α-Sn.

Orange crystals of a Sn14 cluster have been isolated in up to 22% yield from a reaction between Me3SiCH2SnCl3, SnCl4, and LiAlH4. The structure determined by single crystal X-ray diffraction shows three unique Sn atoms in a 6:6:2 ratio, with all Sn atoms 4-coordinate, similar to the tetrahedral bonding in elemental gray Sn. The solid state 117Sn MAS NMR spectrum shows the three types of distinct Sn atoms in the expected 3:3:1 intensity ratio with respective chemical shifts of 87.9, -66.6, and -607.1 ppm relative to Me4Sn. The chemical shift of the two Sn atoms without ligands (bonded only to Sn), at -607.1 ppm, is the most upfield, and is the closest to the chemical shift, reported here, of bulk gray tin (-910 ppm). First-principles density functional theory calculations of the chemical shielding tensors corroborate this assignment. While the core coordination is distorted from the ideal tetrahedral arrangement in the diamond structure of gray tin, this Sn14 cluster, as the largest reported cluster with all 4-coordinate Sn, represents a major incremental step toward being able to prepare atomically precise nanoparticles of gray tin.

Excited-state absorption in tetrapyridyl porphyrins: comparing real-time and quadratic-response time-dependent density functional theory.

Three meso-substituted tetrapyridyl porphyrins (free base, Ni(ii), and Cu(ii)) were investigated for their optical limiting (OL) capabilities using real-time (RT-), linear-response (LR-), and quadratic-response (QR-) time-dependent density functional theory (TDDFT) methods. These species are experimentally known to display a prominent reverse saturable absorption feature between the Q and B bands of the ground-state absorption (GSA), which has been attributed to increased excited-state absorption (ESA) relative to GSA. A recently developed RT-TDDFT based method for calculating ESA from a LR-TDDFT density was utilized with eight exchange-correlation functionals (BLYP, PBE, B3LYP, CAM-B3LYP, PBE0, M06, BHLYP, and BHandH) and contrasted with calculations of ESA using QR-TDDFT with five exchange-correlation functionals (BLYP, B3LYP, CAM-B3LYP, BHLYP, and BHandH). This allowed for comparison between functionals with varying amounts of exact exchange as well as between the ability of RT-TDDFT and QR-TDDFT to reproduce OL behavior in porphyrin systems. The absorption peak positions and intensities for GSA and ESA are significantly impacted by the choice of DFT functional, with the most critical factor identified as the amount of exact exchange in the functional form. Calculating ESA with QR-TDDFT is found to be significantly more sensitive to the amount of exact exchange than GSA and ESA with RT-TDDFT, as well as GSA with LR-TDDFT. An analogous behavior is also demonstrated for the polycyclic aromatic hydrocarbon coronene. This is problematic when using the same approximate functional for calculation of both GSA and ESA, as the LR- and QR-TDDFT excitation energies will not have similar errors. Overall, the RT-TDDFT method with hybrid functionals reproduces the OL features for the porphyrin systems studied here and is a viable computational approach for efficient screening of molecular complexes for OL properties.

Nonequilibrium Chemical Effects in Single-Molecule SERS Revealed by Ab Initio Molecular Dynamics Simulations.

Recent developments in nanophotonics have paved the way for achieving significant advances in the realm of single-molecule chemical detection, imaging, and dynamics. In particular, surface-enhanced Raman scattering (SERS) is a powerful analytical technique that is now routinely used to identify the chemical identity of single molecules. Understanding how nanoscale physical and chemical processes affect single-molecule SERS spectra and selection rules is a challenging task and is still actively debated. Herein, we explore underappreciated chemical phenomena in ultrasensitive SERS. We observe a fluctuating excited electronic state manifold, governed by the conformational dynamics of a molecule (4,4'-dimercaptostilbene, DMS) interacting with a metallic cluster (Ag20). This affects our simulated single-molecule SERS spectra; the time trajectories of a molecule interacting with its unique local environment dictates the relative intensities of the observable Raman-active vibrational states. Ab initio molecular dynamics of a model Ag20-DMS system are used to illustrate both concepts in light of recent experimental results.

Do all men with pathological Gleason score 8-10 prostate cancer have poor outcomes? Results from the SEARCH database.

OBJECTIVE: To determine whether there are subsets of men with pathological high grade prostate cancer (Gleason score 8-10) with particularly high or low 2-year biochemical recurrence (BCR) risk after radical prostatectomy (RP) when stratified into groups based on combinations of pathological features, such as surgical margin status, extracapsular extension (ECE) and seminal vesicle invasion (SVI). MATERIALS AND METHODS: We identified 459 men treated with RP with pathological Gleason score 8-10 prostate cancer in the SEARCH database. The men were stratified into five groups based on pathological characteristics: group 1, men with negative surgical margins (NSMs) and no ECE; group 2, men with positive surgical margin (PSMs) and no ECE; group 3, men with NSMs and ECE; group 4, men with PSMs and ECE; and group 5, men with SVI. Cox proportional hazards models and the log-rank test were used to compare BCR among the groups. RESULTS: At 2 years after RP, pathological group was significantly correlated with BCR (log-rank, P < 0.001) with patients in group 5 (+SVI) having the highest BCR risk (66%) and those in group 1 (NSMs and no ECE) having the lowest risk (14%). When we compared groups 2, 3, and 4, with each other, there was no significant difference in BCR among the groups (~50% 2-year BCR risk; log-rank P = 0.28). Results were similar when adjusting for prostate-specific antigen, age, pathological Gleason sum and clinical stage, or after excluding men who received adjuvant therapy. CONCLUSIONS: In patients with high grade (Gleason score 8-10) prostate cancer after RP, the presence of either PSMs, ECE or SVI was associated with an increased risk of early BCR, with a 2-year BCR risk of ≥50%. Conversely, men with organ-confined margin-negative disease had a very low risk of early BCR despite Gleason score 8-10 disease.

Time-Domain Simulations of Transient Species in Experimentally Relevant Environments.

Simulating the spectroscopic properties of short-lived thermal and photochemical reaction intermediates and products is a challenging task, as these species often feature atypical molecular and electronic structures. The complex environments in which such species typically reside in practice add further complexity to the problem. Herein, we tackle this problem in silico using ab initio molecular dynamics (AIMD) simulations, employing iso-CHBr3, namely H(Br)C-Br-Br, as a prototypical system. This species was chosen because it features both a nonconventional C-Br-Br bonding pattern, as well as a strong dependence of its spectral features on the local environment in which it resides, as illustrated in recent experimental reports. We simulate the UV-vis and IR spectra of iso-CHBr3 in the gas phase, as well as in a Ne cluster (64 atoms) and in a methylcyclohexane cage (14 solvent molecules) representative of the previously characterized matrix isolated and solvated iso-CHBr3 species. We exclusively perform fully quantum mechanical static and dynamic simulations. By comparing our condensed phase simulations to their experimental analogues, we stress the importance of (i) conformational sampling, even at cryogenic temperatures, and (ii) using a fully quantum mechanical description of both solute and bath to properly account for the experimental observables.

Longitudinal Impact of a Family Critical Time Intervention on Children in High-Risk Families Experiencing Homelessness: A Randomized Trial.

A randomized trial compared effects of a Family Critical Time Intervention (FCTI) to usual care for children in 200 newly homeless families in which mothers had diagnosable mental illness or substance problems. Adapted from an evidence-based practice to prevent chronic homelessness for adults with mental illnesses, FCTI combines housing and structured, time-limited case management to connect families leaving shelter with community services. Families were followed at five time points over 24 months. Data on 311 children-99 ages 1.5-5 years, 113 ages 6-10 years, and 99 ages 11-16 years-included mother-, teacher-, and child-reports of mental health, school experiences, and psychosocial well-being. Analyses used hierarchical linear modeling to investigate intervention effects and changes in child functioning over time. Referral to FCTI reduced internalizing and externalizing problems in preschool-aged children and externalizing for adolescents 11-16. The intervention led to declines in self-reported school troubles for children 6-10 and 11-16. Both experimental and control children in all age groups showed reductions in symptoms over time. Although experimental results were scattered, they suggest that FCTI has the potential to improve mental health and school outcomes for children experiencing homelessness.

Associations between building design, point-of-decision stair prompts, and stair use in urban worksites.

OBJECTIVE: Incidental forms of physical activity such as stair use offer frequent opportunities for energy expenditure and may contribute to the prevention and control of chronic diseases. This study analyzes the associations between building characteristics, stair prompts, and stair use in large urban worksites. METHODS: Bootstrapped generalized mixed models were used to analyze self-reported stair use, using data from 1348 surveys of city employees and fourteen building assessments conducted in New York City in 2012. RESULTS: 57% of respondents reported climbing ≥1 flights of stairs daily at the workplace. Model results show that stair prompts were associated with a 3.21 increased likelihood of stair use. Naturally lit stairwells and stairwell visibility were also positively associated. Higher floor residency and BMI were negatively related, as were gender, stairwell distance from lobby entrances, the total number of floors in each building, and building averages for BMI and gender. Residual heterogeneity measured by adjusted median odds ratios indicates that buildings can have a moderate effect on the likelihood of stair use beyond those of individual characteristics. CONCLUSIONS: Specific building features and stair prompts may potentially be leveraged to positively influence rates of incidental physical activity and contribute to improvements in population health.

Non-adiabatic molecular dynamics investigation of photoionization state formation and lifetime in Mn²âº-doped ZnO quantum dots.

The unique electronic structure of Mn(2+)-doped ZnO quantum dots gives rise to photoionization states that can be used to manipulate the magnetic state of the material and to generate zero-reabsorption luminescence. Fast formation and long non-radiative decay of this photoionization state is a necessary requirement for these important applications. In this work, surface hopping based non-adiabatic molecular dynamics are used to demonstrate the fast formation of a metal-to-ligand charge transfer state in a Mn(2+)-doped ZnO quantum dot. The formation occurs on an ultrafast timescale and is aided by the large density of states and significant mixing of the dopant Mn(2+) 3dt2 levels with the valence-band levels of the ZnO lattice. The non-radiative lifetime of the photoionization states is also investigated.

Decoherence-induced surface hopping.

A simple surface hopping method for nonadiabatic molecular dynamics is developed. The method derives from a stochastic modeling of the time-dependent Schrödinger and master equations for open systems and accounts simultaneously for quantum mechanical branching in the otherwise classical (nuclear) degrees of freedom and loss of coherence within the quantum (electronic) subsystem due to coupling to nuclei. Electronic dynamics in the Hilbert space takes the form of a unitary evolution, intermittent with stochastic decoherence events that are manifested as a localization toward (adiabatic) basis states. Classical particles evolve along a single potential energy surface and can switch surfaces only at the decoherence events. Thus, decoherence provides physical justification of surface hopping, obviating the need for ad hoc surface hopping rules. The method is tested with model problems, showing good agreement with the exact quantum mechanical results and providing an improvement over the most popular surface hopping technique. The method is implemented within real-time time-dependent density functional theory formulated in the Kohn-Sham representation and is applied to carbon nanotubes and graphene nanoribbons. The calculated time scales of non-radiative quenching of luminescence in these systems agree with the experimental data and earlier calculations.

The role of surface defects in multi-exciton generation of lead selenide and silicon semiconductor quantum dots.

Multi-exciton generation (MEG), the creation of more than one electron-hole pair per photon absorbed, occurs for excitation energies greater than twice the bandgap (E(g)). Imperfections on the surface of quantum dots, in the form of atomic vacancies or incomplete surface passivation, lead to less than ideal efficiencies for MEG in semiconductor quantum dots. The energetic onset for MEG is computed with and without surface defects for nanocrystals, Pb(4)Se(4), Si(7), and Si(7)H(2). Modeling the correlated motion of two electrons across the bandgap requires a theoretical approach that incorporates many-body effects, such as post-Hartree-Fock quantum chemical methods. We use symmetry-adapted cluster with configuration interaction to study the excited states of nanocrystals and to determine the energetic threshold of MEG. Under laboratory conditions, lead selenide nanocrystals produce multi-excitons at excitation energies of 3 E(g), which is attributed to the large dielectric constant, small Coulomb interaction, and surface defects. In the absence of surface defects the MEG threshold is computed to be 2.6 E(g). For lead selenide nanocrystals with non-bonding selenium valence electrons, Pb(3)Se(4), the MEG threshold increases to 2.9 E(g). Experimental evidence of MEG in passivated silicon quantum dots places the onset of MEG at 2.4 E(g). Our calculations show that the lowest multi-exciton state has an excitation energy of 2.5 E(g), and surface passivation enhances the optical activity of MEG. However, incomplete surface passivation resulting in a neutral radical on the surface drives the MEG threshold to 4.4 E(g). Investigating the mechanism of MEG at the atomistic level provides explanations for experimental discrepancies and suggests ideal materials for photovoltaic conversion.

Surface hopping with Ehrenfest excited potential.

Given the exponentially scaling cost of full quantum calculations, approximations need to be employed for the simulation of the time evolution of chemical systems. We present a modified version of surface hopping that has the potential to treat larger systems. This is accomplished through an Ehrenfest-like treatment of the excited states, thereby reducing the dynamics to transitions between the ground state and a mean-field excited state. A simplified description of the excited states is achieved, while still allowing for an accurate description of disparate reaction channels. We test our mean-field approximation for the excited states on a series of model problems. Results are compared to the standard surface hopping procedure, with its explicit treatment of all excited states, and the traditional Ehrenfest approach, with its averaging together of all states.

Regarding the validity of the time-dependent Kohn-Sham approach for electron-nuclear dynamics via trajectory surface hopping.

The implementation of fewest-switches surface-hopping (FSSH) within time-dependent Kohn-Sham (TDKS) theory [Phys. Rev. Lett. 95, 163001 (2005)] has allowed us to study successfully excited state dynamics involving many electronic states in a variety of molecular and nanoscale systems, including chromophore-semiconductor interfaces, semiconductor and metallic quantum dots, carbon nanotubes and graphene nanoribbons, etc. At the same time, a concern has been raised that the KS orbital basis used in the calculation provides only approximate potential energy surfaces [J. Chem. Phys. 125, 014110 (2006)]. While this approximation does exist in our method, we show here that FSSH-TDKS is a viable option for computationally efficient calculations in large systems with straightforward excited state dynamics. We demonstrate that the potential energy surfaces and nonadiabatic transition probabilities obtained within the TDKS and linear response (LR) time-dependent density functional theories (TDDFT) agree semiquantitatively for three different systems, including an organic chromophore ligating a transition metal, a quantum dot, and a small molecule. Further, in the latter case the FSSH-TDKS procedure generates results that are in line with FSSH implemented within LR-TDDFT. The FSSH-TDKS approach is successful for several reasons. First, single-particle KS excitations often give a good representation of LR excitations. In this regard, DFT compares favorably with the Hartree-Fock theory, for which LR excitations are typically combinations of multiple single-particle excitations. Second, the majority of the FSSH-TDKS applications have been performed with large systems involving simple excitations types. Excitation of a single electron in such systems creates a relatively small perturbation to the total electron density summed over all electrons, and it has a small effect on the nuclear dynamics compared, for instance, with thermal nuclear fluctuations. In such cases an additional, classical-path approximation can be made. Third, typical observables measured in time-resolved experiments involve averaging over many initial conditions. Such averaging tends to cancel out random errors that may be encountered in individual simulated trajectories. Finally, if the flow of energy between electronic and nuclear subsystems is insignificant, the ad hoc FSSH procedure is not required, and a straightforward mean-field, Ehrenfest approach is sufficient. Then, the KS representation provides rigorously a convenient and efficient basis for numerically solving the TDDFT equations of motion.

Structural and theoretical studies of 4-chloro-2-methyl-6-oxo-3,6-dideuteropyrimidin-1-ium chloride (d 6).

The title compound, C5D6ClN2O+·Cl-, crystallizes in the ortho-rhom-bic space group, Pbcm, and consists of a 4-chloro-2-methyl-6-oxo-3,6-di-hydro-pyrimidin-1-ium cation and a chloride anion where both moieties lie on a crystallographic mirror. The cation is disordered and was refined as two equivalent forms with occupancies of 0.750 (4)/0.250 (4), while the chloride anion is triply disordered with occupancies of 0.774 (12), 0.12 (2), and 0.11 (2). Unusually, the bond angles around the C=O unit range from 127.2 (6) to 115.2 (3)° and similar angles have been found in other structures containing a 6-oxo-3,6-di-hydro-pyrimidin-1-ium cation, including the monclinic polymorph of the title compound, which crystallizes in the monoclinic space group P21/c [Kawai et al. (1973 ▸). Cryst. Struct. Comm. 2, 663-666]. The cations and anions pack into sheets in the ab plane linked by N-H⋯Cl hydrogen bonds as well as C-H⋯O and Cl⋯O inter-actions. In graph-set notation, these form R 3 3(11) and R 3 2(9) rings. Theoretical calculations seem to indicate that the reason for the unusual angles at the sp 2 C is the electrostatic inter-action between the oxygen atom and the adjacent N-H hydrogen.

Auditing local news presence on Google News.

Local news outlets have struggled to stay open in the more competitive market of digital media. Some have noted that this decline may be due to the ways in which digital platforms direct attention to some news outlets and not others. To test this theory, we collected 12.29 million responses to Google News searches within all US counties for a set of keywords. We compared the number of local outlets reported in the results against the number of national outlets. We find that, unless consumers are searching specifically for topics of local interest, national outlets dominate search results. Features correlated with local supply and demand, such as the number of local outlets and demographics associated with local news consumption, are not related to the likelihood of finding a local news outlet. Our findings imply that platforms may be diverting web traffic and desperately needed advertising dollars away from local news.

First Principles Nonadiabatic Excited-State Molecular Dynamics in NWChem.

Computational simulation of nonadiabatic molecular dynamics is an indispensable tool for understanding complex photoinduced processes such as internal conversion, energy transfer, charge separation, and spatial localization of excitons, to name a few. We report an implementation of the fewest-switches surface-hopping algorithm in the NWChem computational chemistry program. The surface-hopping method is combined with linear-response time-dependent density functional theory calculations of adiabatic excited-state potential energy surfaces. To treat quantum transitions between arbitrary electronic Born-Oppenheimer states, we have implemented both numerical and analytical differentiation schemes for derivative nonadiabatic couplings. A numerical approach for the time-derivative nonadiabatic couplings together with an analytical method for calculating nonadiabatic coupling vectors is an efficient combination for surface-hopping approaches. Additionally, electronic decoherence schemes and a state reassigned unavoided crossings algorithm are implemented to improve the accuracy of the simulated dynamics and to handle trivial unavoided crossings. We apply our code to study the ultrafast decay of photoexcited benzene, including a detailed analysis of the potential energy surface, population decay timescales, and vibrational coordinates coupled to the excitation dynamics. We also study the photoinduced dynamics in trans-distyrylbenzene. This study provides a baseline for future implementations of higher-level frameworks for simulating nonadiabatic molecular dynamics in NWChem.

Ab initio nonadiabatic molecular dynamics of wet-electrons on the TiO(2) surface.

The electron transfer (ET) dynamics of wet-electrons on a TiO(2) surface is investigated using state-of-the-art ab initio nonadiabatic (NA) molecular dynamics (MD). The simulations directly mimic the time-resolved experiments [Science 2005, 308, 1154] and reveal the nature of ET in the wet-electron system. Focusing on the partially hydroxylated TiO(2) surface with 1-monolayer water coverage, and including electronic evolution, phonon motions, and electron-phonon coupling, the simulations indicate that the ET is sub-10 fs, in agreement with the experiment. Despite the large role played by low frequency vibrational modes, the ET is fast due to the strong coupling between the TiO(2) surface and water. The average ET for the system has equal contributions from the adiabatic and NA mechanisms, even though a very broad range of individual ET events is seen in the simulated ensemble. Thermal phonon motions induce a large fluctuation of the wet-electron state energy, generate frequent crossings of the donor and acceptor states, and drive the adiabatic mechanism. The rapid phonon-assisted NA tunneling from the wet-electron state to the TiO(2) surface is facilitated by the strong water-TiO(2) electronic interaction. The motions of molecular water have a greater effect on the ET dynamics than the hydroxyl vibrations. The former contribute to both the wet-electron state energy and the water-TiO(2) electronic coupling, while the latter changes only the energy and not the coupling. Delocalized over both water and TiO(2), wet-electrons are supported by a new type of state that is created at the interface due to the strong water-TiO(2) interaction and that cannot exist separately in either material. Similar states are present in a number of other systems with strong interfacial coupling, including certain dye-sensitized semiconductors and metal-liquid interfaces. The ET dynamics involving such interfacial states share many universal features, such as an ultrashort time scale and weak-dependence on temperature, surface defects, and other system details.