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Showing papers in "Journal of Physical Chemistry Letters in 2020"


Journal ArticleDOI
Pavlo O. Dral1
TL;DR: A view on the current state of affairs in this new exciting research field is offered, challenges of using ML in QC applications are described, and potential future developments are outlined.
Abstract: As the quantum chemistry (QC) community embraces machine learning (ML), the number of new methods and applications based on the combination of QC and ML is surging. In this Perspective, a view of the current state of affairs in this new and exciting research field is offered, challenges of using machine learning in quantum chemistry applications are described, and potential future developments are outlined. Specifically, examples of how machine learning is used to improve the accuracy and accelerate quantum chemical research are shown. Generalization and classification of existing techniques are provided to ease the navigation in the sea of literature and to guide researchers entering the field. The emphasis of this Perspective is on supervised machine learning.

261 citations


Journal ArticleDOI
TL;DR: This work constructs a new meta-generalized gradient approximation by restoring exact constraint adherence to rSCAN, and maintains r SCAN's numerical performance while restoring the transferable accuracy of SCAN.
Abstract: The recently proposed rSCAN functional [ J. Chem. Phys. 2019 150, 161101] is a regularized form of the SCAN functional [ Phys. Rev. Lett. 2015 115, 036402] that improves SCAN’s numerical performanc...

239 citations


Journal ArticleDOI
TL;DR: Doped lead-free Sb3+-doped Cs2NaInCl6 double perovskites may overcome the bottlenecks of severe toxicity and insufficient stability, and therefore have an extensive application in the scarce blue photonic and optoelectronic fields.
Abstract: Highly efficient blue-emitting three-dimensional (3D) lead-free halide perovskites with excellent stability have attracted worldwide attention. Herein, a doping route was adopted to incorporate Sb3+ ions into the Cs2NaInCl6 for decorating the electronic band structure. Due to the moderate electron-phonon coupling, the Sb3+-doped Cs2NaInCl6 double perovskites showed a narrow and relatively unusual blue emission of self-trapped excitons (STEs). Density functional theory (DFT) calculation indicated that the doped Sb3+ ions could break the parity-forbidden transition rule and modulate the density of state (DOS) population effectively to boost the PLQY of STEs drastically. The optimized Sb3+:Cs2NaInCl6 exhibited a PLQY of up to 75.89% and excellent stability under the consecutive illumination of 365 nm UV light for 1000 h. This kind of highly efficient lead-free Sb3+-doped Cs2NaInCl6 double perovskites may overcome the bottlenecks of severe toxicity and insufficient stability and therefore have an extensive application in the scarce blue photonic and optoelectronic fields.

207 citations


Journal ArticleDOI
TL;DR: In this article, the experimental realization of colloidal particle diffusion and resetting via holographic optical tweezers is reported, and the authors provide the first experimental corroboration of central theoretical results and measure the energetic cost of resetting in steady-state and first-passage scenarios.
Abstract: Stochastic resetting is prevalent in natural and man-made systems, giving rise to a long series of nonequilibrium phenomena. Diffusion with stochastic resetting serves as a paradigmatic model to study these phenomena, but the lack of a well-controlled platform by which this process can be studied experimentally has been a major impediment to research in the field. Here, we report the experimental realization of colloidal particle diffusion and resetting via holographic optical tweezers. We provide the first experimental corroboration of central theoretical results and go on to measure the energetic cost of resetting in steady-state and first-passage scenarios. In both cases, we show that this cost cannot be made arbitrarily small because of fundamental constraints on realistic resetting protocols. The methods developed herein open the door to future experimental study of resetting phenomena beyond diffusion.

153 citations


Journal ArticleDOI
TL;DR: Multi-microsecond-long molecular dynamics simulations enabled us to unprecedentedly dissect the key molecular traits liable of the higher affinity/specificity of SARS-CoV-2 toward ACE2 as compared to SARS -CoV, supplying a minute per-residue contact map underlining its stunningly high infectivity.
Abstract: The severe acute respiratory syndrome coronavirus (SARS-CoV-2) pandemic is setting the global health crisis of our time, causing a devastating societal and economic burden. An idiosyncratic trait of coronaviruses is the presence of spike glycoproteins on the viral envelope, which mediate the virus binding to specific host receptor, enabling its entry into the human cells. In spite of the high sequence identity of SARS-CoV-2 with its closely related SARS-CoV emerged in 2002, the atomic-level determinants underlining the molecular recognition of SARS-CoV-2 to the angiotensin-converting enzyme 2 (ACE2) receptor and, thus, the rapid virus spread into human body, remain unresolved. Here, multi-microsecond-long molecular dynamics simulations enabled us to unprecedentedly dissect the key molecular traits liable of the higher affinity/specificity of SARS-CoV-2 toward ACE2 as compared to SARS-CoV. This supplies a minute per-residue contact map underlining its stunningly high infectivity. Harnessing this knowledge is pivotal for urgently developing effective medical countermeasures to face the ongoing global health crisis.

140 citations


Journal ArticleDOI
TL;DR: The cross-correlation of optical data with DFT calculations evidences the role of octahedral tilting in tailoring the value of the band gap at a given temperature, whereas differences in the thermal expansion affect the slope of theBand gap trend as a function of temperature.
Abstract: Single crystals represent a benchmark for understanding the bulk properties of halide perovskites. We have indeed studied the dielectric function of lead bromide perovskite single crystals (MAPbBr3...

134 citations


Journal ArticleDOI
Tien Huynh1, Haoran Wang, Binquan Luan1
TL;DR: An important ligand binding mechanism of the Mpro is revealed, demonstrating that the binding stability of a ligand inside the M Pro pocket can be significantly improved if part of the ligand occupies its so-called “anchor” site.
Abstract: Currently, the new coronavirus disease 2019 (COVID-19) is a global pandemic without any well-calibrated treatment. To inactivate the SARS-CoV-2 virus that causes COVID-19, the main protease (Mpro) that performs key biological functions in the virus has been the focus of extensive studies. With the fast-response experimental efforts, the crystal structures of Mpro of the SARS-CoV-2 virus have just become available recently. Herein, we theoretically investigated the mechanism of binding between the Mpro's pocket and various marketed drug molecules being tested in clinics to fight COVID-19 that show promising outcomes. By combining the existing experimental results with our computational ones, we revealed an important ligand binding mechanism of the Mpro, demonstrating that the binding stability of a ligand inside the Mpro pocket can be significantly improved if part of the ligand occupies its so-called "anchor" site. Along with the highly potent drugs and/or molecules (such as nelfinavir) revealed in this study, the newly discovered binding mechanism paves the way for further optimizations and designs of Mpro's inhibitors with a high binding affinity.

122 citations


Journal ArticleDOI
TL;DR: It is summarized that the recent studies have revealed that the H–O–H bending mode can be an equally powerful reporter for the microscopic structure of water and provides more direct access to the hydrogen-bonded network than the conventionally studied O–H stretch mode.
Abstract: Insights into the microscopic structure and dynamics of the water's hydrogen-bonded network are crucial to understand the role of water in biology, atmospheric and geochemical processes, and chemical reactions in aqueous systems. Vibrational spectroscopy of water has provided many such insights, in particular using the O-H stretch mode. In this Perspective, we summarize our recent studies that have revealed that the H-O-H bending mode can be an equally powerful reporter for the microscopic structure of water and provides more direct access to the hydrogen-bonded network than the conventionally studied O-H stretch mode. We discuss the fundamental vibrational properties of the water bending mode, such as the intermolecular vibrational coupling, and its effects on the spectral lineshapes and vibrational dynamics. Several examples of static and ultrafast bending mode spectroscopy illustrate how the water bending mode provides an excellent window on the microscopic structure of both bulk and interfacial water.

118 citations


Journal ArticleDOI
TL;DR: It is proposed that a sufficiently long Mn-Mn distance in 0D metal halides enables the all Mn2+ centers emit spontaneously, thereby leading to near-unity photoluminescence quantum yield.
Abstract: Zero-dimensional (0D) Mn2+-based metal halides are potential candidates as narrow-band green emitters, and thus it is critical to provide a structural understanding of the photophysical process. Herein, we propose that a sufficiently long Mn-Mn distance in 0D metal halides enables all Mn2+ centers to emit spontaneously, thereby leading to near-unity photoluminescence quantum yield. Taking lead-free (C10H16N)2Zn1-xMnxBr4 (x = 0-1) solid solution as an example, the Zn/Mn alloying inhibits the concentration quenching that is caused by the energy transfer of Mn2+. (C10H16N)2MnBr4 exhibits highly thermal stable luminescence even up to 150 °C with a narrow-band green emission at 518 nm and a full width at half maximum of 46 nm. The fabricated white light-emitting diode device shows a high luminous efficacy of 120 lm/W and a wide color gamut of 104% National Television System Committee standard, suggesting its potential for liquid crystal displays backlighting. These results provide a guidance for designing new narrow-band green emitters in Mn2+-based metal halides.

114 citations


Journal ArticleDOI
TL;DR: This research represents an important step for developing dual-metal doping NMFC for proton exchange membrane fuel cells (PEMFCs) by revealing its new structural configuration and correlation with catalytic activity.
Abstract: Herein, we synthesized a Fe, Ni dual-metal embedded in porous nitrogen-doped carbon material to endow higher turnover frequency (TOF), lower H2O2 yield, and thus superior durability than for the single-atom catalyst for oxygen reduction in acid media. Quantitative X-ray absorption near edge structure (XANES) fitting and density functional theory (DFT) calculation were implemented to explore the active sites in the catalysts. The results suggest FeNi-N6 with type I (each metal atom coordinated with four nitrogen atoms) instead of type II configuration (each metal atom coordinated with three nitrogen atoms) dominates the catalytic activity of the noble-metal free catalyst (NMFC). Further, theoretical calculation reveals that the oxygen reduction reaction (ORR) activity trend of different moieties was FeNi-N6 (type I) > FeNi-N6 (type II) > Fe-N4 > Fe2-N6. Our research represents an important step for developing dual-metal doping NMFC for proton exchange membrane fuel cells (PEMFCs) by revealing its new structural configuration and correlation with catalytic activity.

114 citations


Journal ArticleDOI
TL;DR: In this article, a phase-free deep learning approach was proposed to simplify the simulation of photodynamic simulations by using rotationally covariant nonadiabatic couplings, which can either be trained or alternatively be approximated from only ML potentials.
Abstract: In recent years, deep learning has become a part of our everyday life and is revolutionizing quantum chemistry as well. In this work, we show how deep learning can be used to advance the research field of photochemistry by learning all important properties-multiple energies, forces, and different couplings-for photodynamics simulations. We simplify such simulations substantially by (i) a phase-free training skipping costly preprocessing of raw quantum chemistry data; (ii) rotationally covariant nonadiabatic couplings, which can either be trained or (iii) alternatively be approximated from only ML potentials, their gradients, and Hessians; and (iv) incorporating spin-orbit couplings. As the deep-learning method, we employ SchNet with its automatically determined representation of molecular structures and extend it for multiple electronic states. In combination with the molecular dynamics program SHARC, our approach termed SchNarc is tested on two polyatomic molecules and paves the way toward efficient photodynamics simulations of complex systems.

Journal ArticleDOI
TL;DR: In this study, the findings of a blind challenge devoted to determining the frozen-core, full configuration interaction (FCI) ground-state energy of the benzene molecule in a standard correlation-consistent basis set of double-ζ quality are reported.
Abstract: We report on the findings of a blind challenge devoted to determining the frozen-core, full configuration interaction (FCI) ground-state energy of the benzene molecule in a standard correlation-consistent basis set of double-ζ quality. As a broad international endeavor, our suite of wave function-based correlation methods collectively represents a diverse view of the high-accuracy repertoire offered by modern electronic structure theory. In our assessment, the evaluated high-level methods are all found to qualitatively agree on a final correlation energy, with most methods yielding an estimate of the FCI value around -863 mEH. However, we find the root-mean-square deviation of the energies from the studied methods to be considerable (1.3 mEH), which in light of the acclaimed performance of each of the methods for smaller molecular systems clearly displays the challenges faced in extending reliable, near-exact correlation methods to larger systems. While the discrepancies exposed by our study thus emphasize the fact that the current state-of-the-art approaches leave room for improvement, we still expect the present assessment to provide a valuable community resource for benchmark and calibration purposes going forward.

Journal ArticleDOI
TL;DR: This work reviews recent advances in constructing high-fidelity potential energy surfaces (PESs) from discrete ab initio points, using machine learning tools and focuses on inelastic and reactive scattering processes, which are more challenging than bound systems because of the involvement of continua.
Abstract: In this Perspective, we review recent advances in constructing high-fidelity potential energy surfaces (PESs) from discrete ab initio points, using machine learning tools. Such PESs, albeit with su...

Journal ArticleDOI
TL;DR: The newly developed stimulated Raman excited fluorescence microscopy is employed to measure the electric field at the water-oil interface of microdroplets and it is suggested that this strong electric field might account in part for the unique properties of chemical reactions reported in micro droplets.
Abstract: Chemical reactions in aqueous microdroplets often exhibit unusual kinetic and thermodynamic properties not observed in bulk solution. While an electric field has been implicated at the water interface, there has been no direct measurement in aqueous microdroplets, largely due to the lack of proper measurement tools. Herein, we employ newly developed stimulated Raman excited fluorescence microscopy to measure the electric field at the water-oil interface of microdroplets. As determined by the vibrational Stark effect of a nitrile-bearing fluorescent probe, the strength of the electric field is found to be on the order of 107 V/cm. This strong electric field aligns probe dipoles with respect to the interface. The formation of the electric field likely arises from charge separation caused by the adsorption of negative ions at the water-oil interface of microdroplets. We suggest that this strong electric field might account in part for the unique properties of chemical reactions reported in microdroplets.

Journal ArticleDOI
TL;DR: A novel lead-free Cu(I) based organic-inorganic perovskite-related material of (MA)4Cu2Br6 single crystal with a zero-dimensional (0D) clusters, which is a unique Cu2Br64- corner-shared tetrahedron dimer structure consisting of two connected tetrahedral clusters.
Abstract: Recently, low-dimensional organic-inorganic lead halide perovskites have attracted a great deal of attention due to their outstanding tunable broadband emission, while the toxicity of lead hinders their further application in the photoelectric field. Here, we report a novel lead-free Cu(I)-based organic-inorganic perovskite-related material of a (MA)4Cu2Br6 single crystal with zero-dimensional clusters, which is a unique Cu2Br64- corner-sharing tetrahedron dimer structure consisting of two connected tetrahedra. The single crystal displays a bright broadband green emission with a high photoluminescence with a quantum yield of ≤93%, a large Stokes shift, and a very long (microsecond) photoluminescence (PL) lifetime, resulting from self-trapped exciton emission. The direct band gap characteristic of (MA)4Cu2Br6 was proven by density functional theory calculation, and its band gap was determined by experiments to be ∼3.87 eV. In the temperature range of 98-258 K, the PL intensity increases gradually with an increase in temperature due to the deep trapping out of strong electro-phonon coupling, while the PL decreases when the temperature increases over 258 K due to phonon scattering. It is worth mentioning that this new material has high chemical and light stability, in contrast to the lead perovskite.

Journal ArticleDOI
TL;DR: A simplified model is described in which the chiral molecule’s spin polarization is enhanced by a spin blockade effect to generate large spin filtering, implying that exchange interactions and Pauli exclusion constraints are an important aspect of CISS.
Abstract: This Perspective discusses recent experiments that bear on the chiral induced spin selectivity (CISS) mechanism and its manifestation in electronic and magnetic properties of chiral molecules and materials. Although the discussion emphasizes newer experiments, such as the magnetization dependence of chiral molecule interactions with ferromagnetic surfaces, early experiments, which reveal the nonlinear scaling of the spin filtering with applied potential, are described also. In many of the theoretical studies, one has had to invoke unusually large spin-orbit couplings in order to reproduce the large spin filtering observed in experiments. Experiments imply that exchange interactions and Pauli exclusion constraints are an important aspect of CISS. They also demonstrate the spin-dependent charge flow between a ferromagnetic substrate and chiral molecules. With these insights in mind, a simplified model is described in which the chiral molecule's spin polarization is enhanced by a spin blockade effect to generate large spin filtering.

Journal ArticleDOI
TL;DR: The combination of decent scintillation performance, low toxicity and good stability, promotes the Rb2CuCl3 as promising X-ray scintillators.
Abstract: Lead halide perovskites have recently shown great potential as X-ray scintillators; however, the toxicity of the lead element seriously restricts their applications. Herein we report a new lead-fre...

Journal ArticleDOI
TL;DR: Two of the top drug hits have significant activity in inhibiting purified recombinant SARS-CoV-2 helicase, providing hope that these drugs can be potentially repurposed for the treatment of COVID-19.
Abstract: The raging COVID-19 pandemic caused by SARS-CoV-2 has infected tens of millions of people and killed several hundred thousand patients worldwide. Currently, there are no effective drugs or vaccines...

Journal ArticleDOI
TL;DR: Double-layered PM-OPDs with the structure of ITO/ZnO/PM6:Y6/PC71BM:P3HT (100:5, wt/wt)/Au are designed and exhibit broad response covering 350-950 nm and the largest EQE value of ~1200% and the maximum specific detectivity of ~6.8 × 10-12 cm Hz1/2 W-1 under 10 V bias are presented.
Abstract: Broad response organic photodetectors (OPDs) with a photomultiplication (PM) effect are achieved with one absorber layer and one multiplication layer. The response range of the PM-OPDs is primarily determined by materials in the absorber layer, and the external quantum efficiency (EQE) of the PM-OPDs is mainly controlled by the multiplication layer. Here, double-layered PM-OPDs were designed with an ITO/ZnO/PM6:Y6/PC71BM:P3HT (100:5, w/w)/Au structure, where PM6:Y6 is employed as an absorber layer and PC71BM:P3HT is used as a multiplication layer. The optimal PM-OPDs exhibit a broad response covering 350-950 nm. Meanwhile, the optimal PM-OPDs exhibit the largest EQE value of ∼1200% and a maximum specific detectivity (D*) of ∼6.8 × 10-12 cm Hz1/2 W-1 under a 10 V bias. This double-layered approach may be a smart strategy for realizing PM-OPDs with an easily adjustable response range.

Journal ArticleDOI
TL;DR: It is shown that the inherently low ionization potential of MASnI3 is solely responsible of the high stability of tin vacancy and interstitial iodine defects, which are in turn at the origin of the material p-doping, and tin chemistry dominates tin-iodide perovskites defect chemistry.
Abstract: Tin halide perovskites make up the only lead-free material class endowed with optoelectronic properties comparable to those of lead iodide perovskites. Despite significant progress, the device effi...

Journal ArticleDOI
TL;DR: Red-emissive carbon quantum dots are reported, which can enter into the nuclei of not only cancer cells but also cancer stem cells, which provides a potential strategy for developing carbon quantum-dot-based anticancer drug carriers for effective eradication of cancers.
Abstract: Large doses of anticancer drugs entering cancer cell nuclei are found to be effective at killing cancer cells and increasing chemotherapeutic effectiveness. Here we report red-emissive carbon quantum dots, which can enter into the nuclei of not only cancer cells but also cancer stem cells. After doxorubicin was loaded at the concentration of 30 μg/mL on the surfaces of carbon quantum dots, the average cell viability of HeLa cells was decreased to only 21%, while it was decreased to 50% for free doxorubicin. The doxorubicin-loaded carbon quantum dots also exhibited a good therapeutic effect by eliminating cancer stem cells. This work provides a potential strategy for developing carbon quantum-dot-based anticancer drug carriers for effective eradication of cancers.

Journal ArticleDOI
TL;DR: The current state of the field is discussed by summarizing the most extensively studied carrier transport mechanisms such as electron-phonon scattering limited dynamics, ferroelectric effects, Rashba-type band splitting, and polaronic transport.
Abstract: Metal halide perovskites (MHPs) have rapidly emerged as leading contenders in photovoltaic technology and other optoelectronic applications owing to their outstanding optoelectronic properties. After a decade of intense research, an in-depth understanding of the charge carrier transport in MHPs is still an active topic of debate. In this Perspective, we discuss the current state of the field by summarizing the most extensively studied carrier transport mechanisms, such as electron-phonon scattering limited dynamics, ferroelectric effects, Rashba-type band splitting, and polaronic transport. We further extensively discuss the emerging experimental and computational evidence for dominant polaronic carrier dynamics in MHPs. Focusing on both small and large polarons, we explore the fundamental aspects of their motion through the lattice, protecting the photogenerated charge carriers from the recombination process. Finally, we outline different physical and chemical approaches considered recently to study and exploit the polaron transport in MHPs.

Journal ArticleDOI
TL;DR: The results indicate that it is implausible for the SARS-CoV-2 to be a lab-engineered virus, and the enhancement in the binding energy is not due to a single mutant but rather because of the sophisticated structural changes induced by all these mutations together.
Abstract: SARS-CoV-2, since emerging in Wuhan, China, has been a major concern because of its high infection rate and has left more than six million infected people around the world. Many studies endeavored to reveal the structure of the SARS-CoV-2 compared to the SARS-CoV, in order to find solutions to suppress this high infection rate. Some of these studies showed that the mutations in the SARS-CoV spike (S) protein might be responsible for its higher affinity to the ACE2 human cell receptor. In this work, we used molecular dynamics simulations and Monte Carlo sampling to compare the binding affinities of the S proteins of SARS-CoV and SARS-CoV-2 to the ACE2. Our results show that the protein surface of the ACE2 at the receptor binding domain (RBD) exhibits negative electrostatic potential, while a positive potential is observed for the S proteins of SARS-CoV/SARS-CoV-2. In addition, the binding energies at the interface are slightly higher for SARS-CoV-2 because of enhanced electrostatic interactions. The major contributions to the electrostatic binding energies result from the salt bridges forming between R426 and ACE-2-E329 in the case of SARS-CoV and K417 and ACE2-D30 in the SARS-CoV-2. In addition, our results indicate that the enhancement in the binding energy is not due to a single mutant but rather because of the sophisticated structural changes induced by all these mutations together. This finding suggests that it is implausible for the SARS-CoV-2 to be a lab-engineered virus.

Journal ArticleDOI
TL;DR: An overview of the successive steps that made possible to obtain increasingly accurate excitation energies with computational chemistry tools, eventually leading to chemically accurate vertical transition energies for small- and medium-size molecules.
Abstract: We provide an overview of the successive steps that made it possible to obtain increasingly accurate excitation energies with computational chemistry tools, eventually leading to chemically accurate vertical transition energies for small- and medium-size molecules. First, we describe the evolution of ab initio methods employed to define benchmark values, with the original Roos CASPT2 method, then the CC3 method as in the renowned Thiel set, and more recently the resurgence of selected configuration interaction methods. The latter method has been able to deliver consistently, for both single and double excitations, highly accurate excitation energies for small molecules, as well as medium-size molecules with compact basis sets. Second, we describe how these high-level methods and the creation of representative benchmark sets of excitation energies have allowed the fair and accurate assessment of the performance of computationally lighter methods. We conclude by discussing possible future theoretical and technological developments in the field.

Journal ArticleDOI
TL;DR: Liquid formic acid (LFA) was introduced as a reducing solvent in the FASnI3 (FA: formamidinium) perovskite precursor solution, and an efficiency of over 10% was obtained for lead-free tin halide PSCs with improved reproducibility.
Abstract: Lead-free tin halide perovskite solar cells (PSCs) have attracted great attention because of their low toxicity, ideal band gap, and high carrier mobilities. However, the efficiency and reproducibility of tin halide PSCs has been limited because of the facile oxidation of Sn2+ to Sn4+. Herein, liquid formic acid (LFA) was introduced as a reducing solvent in the FASnI3 (FA: formamidinium) perovskite precursor solution. Unlike solid reducing additives, the LFA solvent is volatile, so no residual LFA remained in the FASnI3 perovskite film. Use of the LFA solvent resulted in production of the FASnI3 perovskite film with high crystallinity, low Sn4+ content, reduced background doping, and low electronic trap density. As a result, an efficiency of over 10% was obtained for lead-free tin halide PSCs with improved reproducibility.

Journal ArticleDOI
TL;DR: A change in perspective is proposed that shifts the focus from the bias to the probability distribution reconstruction, while keeping some of the key characteristics of metadynamics, such as the flexible on-the-fly adjustments to the free energy estimate.
Abstract: Metadynamics is an enhanced sampling method of great popularity, based on the on-the-fly construction of a bias potential that is a function of a selected number of collective variables. We propose here a change in perspective that shifts the focus from the bias to the probability distribution reconstruction while retaining some of the key characteristics of metadynamics, such as flexible on-the-fly adjustments to the free energy estimate. The result is an enhanced sampling method that presents a drastic improvement in convergence speed, especially when dealing with suboptimal and/or multidimensional sets of collective variables. The method is especially robust and easy to use and in fact requires only a few simple parameters to be set, and it has a straightforward reweighting scheme to recover the statistics of the unbiased ensemble. Furthermore, it gives more control of the desired exploration of the phase space since the deposited bias is not allowed to grow indefinitely and it does not push the simulation to uninteresting high free energy regions. We demonstrate the performance of the method in a number of representative examples.

Journal ArticleDOI
TL;DR: It is argued that an interplay of long-range and short-range exciton-lattice couplings give rise to exciton polarons, which fundamentally establishes their effective mass and radius, and consequently, their quantum dynamics.
Abstract: While polarons --- charges bound to a lattice deformation induced by electron-phonon coupling --- are primary photoexcitations in bulk metal-halide hybrid organic-inorganic perovskites (HOIP), exci...

Journal ArticleDOI
TL;DR: In this paper, a large set of descriptors and neural networks are employed to compress the information in a lower-dimensional space, using Fisher's linear discriminant as an objective function to maximize the discriminative power.
Abstract: Designing an appropriate set of collective variables is crucial to the success of several enhanced sampling methods. Here we focus on how to obtain such variables from information limited to the metastable states. We characterize these states by a large set of descriptors and employ neural networks to compress this information in a lower-dimensional space, using Fisher's linear discriminant as an objective function to maximize the discriminative power of the network. We test this method on alanine dipeptide, using the nonlinearly separable data set composed by atomic distances. We then study an intermolecular aldol reaction characterized by a concerted mechanism. The resulting variables are able to promote sampling by drawing nonlinear paths in the physical space connecting the fluctuations between metastable basins. Lastly, we interpret the behavior of the neural network by studying its relation to the physical variables. Through the identification of its most relevant features, we are able to gain chemical insight into the process.

Journal ArticleDOI
TL;DR: A historical overview of BSE is provided, with a particular focus on its condensed-matter roots, and a critical review of its strengths and weaknesses in different chemical situations is proposed.
Abstract: The many-body Green's function Bethe-Salpeter equation (BSE) formalism is steadily asserting itself as a new efficient and accurate tool in the ensemble of computational methods available to chemists in order to predict optical excitations in molecular systems In particular, the combination of the so-called $GW$ approximation of many-body perturbation theory, giving access to reliable ionization energies and electron affinities, and the BSE formalism, able to model UV/Vis spectra by catching excitonic effects, has shown to provide accurate singlet excitation energies in many chemical scenarios with a typical error of $01$--$03$ eV With a similar computational cost as time-dependent density-functional theory (TD-DFT), the BSE formalism is able to provide an accuracy on par with the most accurate global and range-separated hybrid functionals without the unsettling choice of the exchange-correlation functional, resolving further known issues (eg, charge-transfer excitations) and offering a well-defined path to dynamical kernels In this \textit{Perspective} article, we provide a historical overview of the BSE formalism, with a particular focus on its condensed-matter roots We also propose a critical review of its strengths and weaknesses in different chemical situations Future directions of developments and improvements are also discussed

Journal ArticleDOI
TL;DR: Piezoelectric materials are demonstrated as a new source of sonodynamic sensitizers and BP nanosheet suggested as an excellent sensitizer for tumor sonodynamic therapy, thereby suppressing tumor growth and metastasis without causing off-target toxicity in tumor-bearing mouse models.
Abstract: Sonodynamic therapy eliminates cancer cells with reactive oxygen species (ROS) triggered by ultrasound whose energy is spatiotemporally controllable, is safe to human tissues and organs, and penetrates deeply through tissues. Its application, however, is hindered by the scarcity of sonodynamic sensitizers. We herein demonstrate piezoelectric materials as a new source of sonodynamic sensitizers, using few-layer black phosphorus (BP) nanosheet as a model. BP nanosheet exhibited ultrasound-excited cytotoxicity to cancer cells via ROS generation, thereby suppressing tumor growth and metastasis without causing off-target toxicity in tumor-bearing mouse models. The ultrasonic wave introduces mechanical strain to the BP nanosheet, leading to piezoelectric polarization which shifts the conduction band of BP more negative than O2/·O2- while its valence band more positive than H2O/·OH, thereby accelerating the ROS production. This work identifies a new mechanism for discovering sonodynamic sensitizers and suggests BP nanosheet as an excellent sensitizer for tumor sonodynamic therapy.