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Journal of Physical Chemistry Letters

Pavithra Madhavi Naullage, Yuqing Qiu, Valeria Molinero
Cold-adapted organisms produce antifreeze proteins and glycoproteins to control the growth, melting and recrystallization of ice. It has been proposed that these molecules pin the crystal surface, creating a surface curvature that arrests its growth and melting. Here we use thermodynamic modeling and molecular simulations to elucidate how does the curvature of the metastable ice front depend on the temperature and distance between pinned molecules, and what determines the thermal hysteresis on melting and freezing, i...
March 15, 2018: Journal of Physical Chemistry Letters
Luc Belloni, Daniel Borgis, Maximilien Levesque
The ion-induced long-range orientational order between water molecules recently observed in second harmonic scattering experiments and illustrated with large scale molecular dynamics simulations is quantitatively explained using the Ornstein-Zernike integral equation approach of liquid physics. This general effect, not specific to hydrogen-bonding solvents, is controlled by electroneutrality condition, dipolar interactions and dielectric+ionic screening. As expected, all numerical theories recover the well-known analytical expressions established 40 years ago...
March 15, 2018: Journal of Physical Chemistry Letters
Elliot J Taffet, Yoann Olivier, Frankie Lam, David Beljonne, Gregory D Scholes
We report three characteristics of ideal thermally activated delayed fluorescence molecular systems apparent in carbene-metal-amides: (a) an exceptionally small singlet-triplet gap that effectively eliminates the thermal activation barrier to reverse intersystem crossing; (b) significant singlet oscillator strength promoting fluorescence in the region of this small barrier; and (c) enlarged spin-orbit coupling driving reverse intersystem crossing in this region. We carry out highly correlated quantum-chemical calculations to detail the relative energies of and spin-orbit couplings between the singlet and triplet states, finding that they fall closer together in energy and couple more strongly in going from the singlet ground-state to the triplet optimized geometry...
March 15, 2018: Journal of Physical Chemistry Letters
Štěpán Timr, Jan Kadlec, Pavel Srb, O H Samuli Ollila, Pavel Jungwirth
The detailed functional mechanism of recoverin, which acts as a myristoyl switch at the rod outer-segment disk membrane, is elucidated by direct and replica-exchange molecular dynamics. In accord with NMR structural evidence and calcium binding assays, simulations point to the key role of enhanced calcium binding to the EF3 loop of the semiopen state of recoverin as compared to the closed state. This 2-4-order decrease in calcium dissociation constant stabilizes the semiopen state in response to the increase of cytosolic calcium concentration in the vicinity of recoverin...
March 15, 2018: Journal of Physical Chemistry Letters
Elinor Zerah-Harush, Yonatan Dubi
Environment-assisted quantum transport (ENAQT) is the possibility of an external environment to enhance transport efficiency of quantum particles. This idea has generated much excitement over recent years, especially due to the experimentally-motivated possibility of ENAQT in photo-synthetic exciton transfer complexes. Many theoretical calculations have shown ENAQT, but the explanations for its origin differ, and a universal explanation has been elusive. Here we demonstrate a universal origin for ENAQT in quantum networks with a dephasing environment, based on a relation between exciton current and occupation within a Markovian open quantum system approach...
March 14, 2018: Journal of Physical Chemistry Letters
Ravi Kumar Venkatraman, Surajit Kayal, Arvind Barak, Andrew J Orr-Ewing, Siva Umapathy
Solvation plays a critical role in various physicochemical and biological processes. Here, the rate of intersystem crossing (ISC) of benzophenone from its S1(nπ*) state to its triplet manifold of states is shown to be modified by hydrogen-bonding interactions with protic solvent molecules. We selectively photo-excite benzophenone with its carbonyl group either solvent coordinated or uncoordinated by tuning the excitation wavelength to the band center (λ = 340 nm) or the long-wavelength edge (λ = 380 nm) of its π*←n absorption band...
March 14, 2018: Journal of Physical Chemistry Letters
Luis M Pazos Outón, T Patrick Xiao, Eli Yablonovitch
Lead halide materials have seen a recent surge of interest from the photovoltaics community following the observation of surprisingly high photovoltaic performance, with opto-electronic properties similar to GaAs. This begs the question; what is the limit for the efficiency of these materials? It has been known that at 1-sun the efficiency limit of crystalline silicon is ~29%, despite the Shockley-Queisser (SQ) limit for its bandgap being ~33%, the discrepancy being due to strong Auger recombination. In this article, we show that Methyl Ammonium Lead Iodide (MAPbI3) likewise has a larger than expected Auger coefficient...
March 14, 2018: Journal of Physical Chemistry Letters
Nozomi Ito, Muhammad Akmal Kamarudin, Yaohong Zhang, Daisuke Hirotani, Qing Shen, Yuhei Ogomi, Satoshi Iikubo, Takashi Minemoto, Kenji Yoshino, Shuzi Hayase
Lead-based solar cells have gained ground in recent years, showing efficiency as high as 20 % which is on par with silicon solar cells. However, the toxicity of lead makes it non ideal candidate in solar cells. Alternatively, tin-based perovskites have been proposed due to their non-toxic nature and abundance in nature. Unfortunately, these solar cells suffer from low efficiency and stability. Here, we propose a new type of perovskite material based on mixed tin and germanium. The material showed a band gap around 1...
March 14, 2018: Journal of Physical Chemistry Letters
Dominique Laniel, Gunnar Weck, Gabriel Gaiffe, Gaston Garbarino, Paul Loubeyre
Polynitrogen compounds have been actively pursued driven by their potential as ultra-high performing propellants or explosives. Despite remarkable breakthroughs over the past two decades, the two figures of merit for a compelling material, namely a large fraction of nitrogen by weight and a bulk stability at ambient conditions, have not been achieved yet. Here, we report the synthesis of a lithium pentazolate solid by compressing and laser-heating lithium embedded in molecular N2 around 45 GPa along with its recovery at ambient conditions...
March 13, 2018: Journal of Physical Chemistry Letters
Bhupal Kattel, Liang Qin, Tika R Kafle, Wai-Lun Chan
In organic and low-dimensional materials, electrons and holes are bound together to form excitons. Effective exciton dissociation at interfaces is essential for applications such as photovoltaics and photosensing. Here, we present an interface-sensitive, time-resolved method that utilizes graphene field effect transistor as an electric-field sensor to measure the charge separation dynamics and yield at donor-acceptor interfaces. Compared to other interface-sensitive spectroscopy techniques, our method has a much reduced measurement time and can be easily adapted to different material interfaces...
March 13, 2018: Journal of Physical Chemistry Letters
Qiyi Fang, Qiu Yu Shang, Liyun Zhao, Rui Wang, Zhepeng Zhang, Pengfei Yang, Xinyu Sui, Xiaohui Qiu, Xinfeng Liu, Qing Zhang, Yanfeng Zhang
Mixed-dimensional van der Walls heterostructures between one dimensional (1D) perovskite nanowires and two dimensional (2D) transition metal dichalcogenides (TMDCs) hold great potentials for novel optoelectronics and light harvesting applications. However, the ultrafast carrier dynamics between the 1D perovskite and 2D TMDCs is currently not well understood, which is critical for related optoelectronic applications. Here we demonstrate van der Walls heterostructures of CsPbBr3 nanowire/monolayer-MoS2 and CsPbBr3/monolayer-WSe2 and further present systematic investigation on their charge transfer dynamics...
March 13, 2018: Journal of Physical Chemistry Letters
Guoqing Tong, Huan Li, Zhifeng Zhu, Yan Zhang, Linwei Yu, Jun Xu, Yang Jiang
Hybrid perovskite photodetectors (PDs) exhibit outstanding performance in the ultraviolet-visible (UV-vis) spectrum but have poor detectability in the deep ultraviolet (DUV) region (200-350 nm). In this work, a novel inorganic-hybrid architecture that incorporates a dual-phase (CsPbBr3-Cs4PbBr6) inorganic perovskite material as a down-conversion window layer and a hybrid perovskite as light capture layer was prepared to achieve faster, highly sensitive photodetection in the DUV spectrum. A dual-phase inorganic perovskite film coated on the back surface of photodetector enables strong light absorption and tunes the incident energy into emission bands that are optimized for the perovskite photodetector...
March 13, 2018: Journal of Physical Chemistry Letters
Lukas Nico Wirz, Maria Dimitrova, Heike Fliegl, Dage Sundholm
The topology of twisted molecular rings is characterized by the linking number, which is equal to the sum of the twist and writhe parameters. The twist is associated with the local twisting of the molecular frame, whereas the writhe is a global property of the molecular ring. The writhe represents the bending of the molecular ring, which increases π-electron stabilization as well as steric interactions and reduces the strain of twisted molecular rings. In this work, we investigate a number of cyclic all-trans C40 H40 annulenes with different topologies and their dications...
March 13, 2018: Journal of Physical Chemistry Letters
Ya Zhuo, Aria Mansouri Tehrani, Jakoah Brgoch
A machine-learning model is developed that can accurately predict the band gap of inorganic solids based only on composition. This method uses support vector classification to first separate metals from non-metals, followed by quantitatively predicting the band gap of the non-metals using support vector regression. The superb accuracy of the regression model is obtained by using a training set is composed entirely of experimentally measured band gaps and utilizing only compositional descriptors. In fact, because of the unique training set of experimental data, the machine learning predicted band gaps are significantly closer to the experimentally reported values than DFT (PBE-level) calculated band gaps...
March 13, 2018: Journal of Physical Chemistry Letters
Swapnil C Kohale, Subha Pratihar, William L Hase
Classical chemical dynamics simulation results are presented for the thermal desorption kinetics and energetics of protonated dialanine ions (ala2 -H+ ) physisorbed on/in a perfluorinated self-assembled monolayer (F-SAM) surface. Previously developed analytic potentials were used for the F-SAM and the ala2 -H+ /F-SAM intermolecular interaction, and the AMBER valence force field was used for ala2 -H+ . The activation energy, Ea = 13.2 kcal/mol, determined from the simulations is consistent with previous simulations of the ala2 -H+ /F-SAM binding energy...
March 13, 2018: Journal of Physical Chemistry Letters
Sucheol Shin, Adam P Willard
We present a simple model of aqueous interfacial molecular structure and we use this model to isolate the effects of hydrogen bonding on the dielectric properties of the liquid water-vapor interface. We show that water?s interfacial molecular structure can be understood by considering the orientational preferences of a single molecule immersed in the environment of the average interfacial density field. We illustrate that depth dependent orientational anisotropy is determined by the geometric constraints of hydrogen bonding and we show that the primary features of atomistic simulation data can be reproduced by assuming an idealized, perfectly tetrahedral hydrogen bonding geometry...
March 12, 2018: Journal of Physical Chemistry Letters
Carla Andreani, Giovanni Romanelli, Roberto Senesi
No abstract text is available yet for this article.
March 12, 2018: Journal of Physical Chemistry Letters
Vikram Sundar, David Gelbwaser-Klimovsky, Alán Aspuru-Guzik
Modeling nuclear quantum effects is required for accurate molecular dynamics (MD) simulations of molecules. The community has paid special attention to water and other biomolecules that show hydrogen bonding. Standard methods of modeling nuclear quantum effects like Ring Polymer Molecular Dynamics (RPMD) are computationally costlier than running classical trajectories. A force-field functor (FFF) is an alternative method that computes an effective force field which replicates quantum properties of the original force field...
March 12, 2018: Journal of Physical Chemistry Letters
Paul Spiering, Joerg Meyer
At present, molecular dynamics with electronic friction (MDEF) is the workhorse model to go beyond the Born-Oppenheimer approximation in modeling dynamics of molecules at metal surfaces. Concomitant friction coefficients can be calculated with either the local density friction approximation (LDFA) or orbital-dependent friction (ODF), which -- unlike LDFA -- accounts for anisotropy while relying on other approximations. Statistically converged observables for diatomics on static surfaces including all degrees of freedom have hitherto only been calculated with LDFA due to the computational cost of ODF...
March 12, 2018: Journal of Physical Chemistry Letters
Ananth Govind Rajan, Michael S Strano, Daniel Blankschtein
Hexagonal boron nitride (hBN) is an upcoming 2D material, with applications in electronic devices, tribology, and separation membranes. Herein, we utilize density-functional-theory-based ab initio molecular dynamics (MD) simulations and lattice dynamics calculations to develop a classical force field (FF) for modeling hBN. The FF predicts the crystal structure, elastic constants, and phonon dispersion relation of hBN with good accuracy, and exhibits remarkable agreement with the interlayer binding energy predicted by random phase approximation calculations...
March 12, 2018: Journal of Physical Chemistry Letters
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