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Journal of Chemical Physics

Julien Steffen, Bernd Hartke
Building on the recently published quantum-mechanically derived force field (QMDFF) and its empirical valence bond extension, EVB-QMDFF, it is now possible to generate a reliable potential energy surface for any given elementary reaction step in an essentially black box manner. This requires a limited and pre-defined set of reference data near the reaction path and generates an accurate approximation of the reference potential energy surface, on and off the reaction path. This intermediate representation can be used to generate reaction rate data, with far better accuracy and reliability than with traditional approaches based on transition state theory (TST) or variational extensions thereof (VTST), even if those include sophisticated tunneling corrections...
October 28, 2017: Journal of Chemical Physics
Mojtaba Alipour, Niloofar Karimi
Organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters are an attractive category of materials that have witnessed a booming development in recent years. In the present contribution, we scrutinize the accountability of parameterized and parameter-free single-hybrid (SH) and double-hybrid (DH) functionals through the two formalisms, full time-dependent density functional theory (TD-DFT) and Tamm-Dancoff approximation (TDA), for the estimation of photophysical properties like absorption energy, emission energy, zero-zero transition energy, and singlet-triplet energy splitting of TADF molecules...
June 21, 2017: Journal of Chemical Physics
G P Johari, Ove Andersson
We report a study of structural relaxation of high-density glasses of di-n-butyl phthalate (DBP) by measuring thermal conductivity, κ, under conditions of pressure and temperature (p,T) designed to modify both the vibrational and configurational states of a glass. Various high-density glassy states of DBP were formed by (i) cooling the liquid under a fixed high p and partially depressurizing the glass, (ii) isothermal annealing of the depressurized glass, and (iii) pressurizing the glass formed by cooling the liquid under low p...
June 21, 2017: Journal of Chemical Physics
Xiaofeng F Duan, Larry W Burggraf
Excited state properties of chain and cyclic oligomers of closo-Si12C12 moieties are calculated using time-dependent density functional theory methods. Ultraviolet, visible, and near-infrared photo-absorption properties are described for oligomers that form by linking closo-Si12C12 monomer moieties through Si-Si bonds. Natural transition orbitals for electron and hole states of stationary-state excitons in oligomers were compared to understand how exciton states are influenced by oligomer structure. Depending on the structure, some prominent excited states have large electron-hole charge separation while others do not; some exhibit exciton delocalization while others do not...
June 21, 2017: Journal of Chemical Physics
Guocai Tian, Yuxiang Mo, Jianmin Tao
Excitation energy plays an important role in energy conversion, biological processes, and optical devices. In this work, we apply the Tao-Mo (TM) nonempirical meta-generalized gradient approximation and the combination TMTPSS (TMx + TPSSc), with TPSSc being the correlation part of the original TPSS (Tao-Perdew-Staroverov-Scuseria) to study excitation energies of small molecules and oligomers. Our test set consists of 17 molecules with 134 total excited states, including singlet, triplet, valence, and Rydberg excited states...
June 21, 2017: Journal of Chemical Physics
Yansun Yao, Elissaios Stavrou, Alexander F Goncharov, Arnab Majumdar, Hui Wang, Vitali B Prakapenka, Albert Epshteyn, Andrew P Purdy
A combined theoretical and experimental study of lithium palladium deuteride (Li2PdD2) subjected to pressures up to 50 GPa reveals one structural phase transition near 10 GPa, detected by synchrotron powder x-ray diffraction, and metadynamics simulations. The ambient-pressure tetragonal phase of Li2PdD2 transforms into a monoclinic C2/m phase that is distinct from all known structures of alkali metal-transition metal hydrides/deuterides. The structure of the high-pressure phase was characterized using ab initio computational techniques and from refinement of the powder x-ray diffraction data...
June 21, 2017: Journal of Chemical Physics
Guillaume Jeanmairet, Sandeep Sharma, Ali Alavi
No abstract text is available yet for this article.
June 21, 2017: Journal of Chemical Physics
Kono H Lemke
This study presents results for the binding energy and geometry of the H2S dimer which have been computed using Møller-Plesset perturbation theory (MP2, MP4) and coupled cluster (CCSD, CCSD(T)) calculations with basis sets up to aug-cc-pV5Z. Estimates of De, EZPE, Do, and dimer geometry have been obtained at each level of theory by taking advantage of the systematic convergence behavior toward the complete basis set (CBS) limit. The CBS limit binding energy values of De are 1.91 (MP2), 1.75 (MP4), 1.41 (CCSD), and 1...
June 21, 2017: Journal of Chemical Physics
Anja Aarva, Tomi Laurila, Miguel A Caro
In this work, we study the adsorption characteristics of dopamine (DA), ascorbic acid (AA), and dopaminequinone (DAox) on carbonaceous electrodes. Our goal is to obtain a better understanding of the adsorption behavior of these analytes in order to promote the development of new carbon-based electrode materials for sensitive and selective detection of dopamine in vivo. Here we employ density functional theory-based simulations to reach a level of detail that cannot be achieved experimentally. To get a broader understanding of carbonaceous surfaces with different morphological characteristics, we compare three materials: graphene, diamond, and amorphous carbon (a-C)...
June 21, 2017: Journal of Chemical Physics
Matthew S Church, Sergey V Antipov, Nandini Ananth
The Mixed Quantum-Classical Initial Value Representation (MQC-IVR) is a recently introduced approximate semiclassical (SC) method for the calculation of real-time quantum correlation functions. MQC-IVR employs a modified Filinov filtration (MFF) scheme to control the overall phase of the SC integrand, extending the applicability of SC methods to complex systems while retaining their ability to accurately describe quantum coherence effects. Here, we address questions regarding the effectiveness of the MFF scheme in combination with SC dynamics...
June 21, 2017: Journal of Chemical Physics
Alberto Fraccarollo, Lorenzo Canti, Leonardo Marchese, Maurizio Cossi
This article describes the structure and the electronic properties of a series of layered perovskites of a general formula (A(+))2(SnX4)(-2) where X = I, Br and A(+) is an organic cation, either formamidinium, 1-methylimidazolium, or phenylethylammonium. For each system, two conformations are considered, with eclipsed or staggered stacking of the adjacent inorganic layers. Geometry optimizations are performed at the density functional theory level with generalized gradient approximation (GGA) functional and semiempirical correction for dispersion energies; band profiles and bandgaps are computed including both spin orbit coupling (SOC) and correlation (GW) effects through an additive scheme...
June 21, 2017: Journal of Chemical Physics
Andrew Mahler, Benjamin G Janesko, Salvador Moncho, Edward N Brothers
"Jacob's Ladder" of approximate exchange-correlation (XC) functionals in Kohn-Sham density functional theory are widely accepted to have systematic errors in reaction barriers. The first-rung local spin-density approximation (LDA) typically predicts barriers below generalized gradient approximations, which in turn predict barriers below experiment and below fourth-rung hybrid functionals incorporating a fraction of exact exchange. We show that several reactions from previous literature reports, as well as new simulations of carbon-carbon coupling in the Fischer-Tropsch process, do not follow this conventional picture...
June 21, 2017: Journal of Chemical Physics
Abdenacer Idrissi, Bogdan A Marekha, Mohammed Barj, François Alexandre Miannay, Toshiyuki Takamuku, Vasilios Raptis, Jannis Samios, Pál Jedlovszky
The information about the structure of dimethyl sulfoxide (DMSO)-water mixtures at relatively low DMSO mole fractions is an important step in order to understand their cryoprotective properties as well as the solvation process of proteins and amino acids. Classical MD simulations, using the potential model combination that best reproduces the free energy of mixing of these compounds, are used to analyze the local structure of DMSO-water mixtures at DMSO mole fractions below 0.2. Significant changes in the local structure of DMSO are observed around the DMSO mole fraction of 0...
June 21, 2017: Journal of Chemical Physics
Alec F White, Evgeny Epifanovsky, C William McCurdy, Martin Head-Gordon
The method of complex basis functions is applied to molecular resonances at correlated levels of theory. Møller-Plesset perturbation theory at second order and equation-of-motion electron attachment coupled-cluster singles and doubles (EOM-EA-CCSD) methods based on a non-Hermitian self-consistent-field reference are used to compute accurate Siegert energies for shape resonances in small molecules including N2(-), CO(-), CO2(-), and CH2O(-). Analytic continuation of complex
June 21, 2017: Journal of Chemical Physics
Alan Sam, Sridhar Kumar Kannam, Remco Hartkamp, Sarith P Sathian
Although the importance of temperature control in nonequilibrium molecular dynamics simulations is widely accepted, the consequences of the thermostatting approach in the case of strongly confined fluids are underappreciated. We show the strong influence of the thermostatting method on the water transport in carbon nanotubes (CNTs) by considering simulations in which the system temperature is controlled via the walls or via the fluid. Streaming velocities and mass flow rates are found to depend on the tube flexibility and on the thermostatting algorithm, with flow rates up to 20% larger when the walls are flexible...
June 21, 2017: Journal of Chemical Physics
C Z Qiao, S L Zhao, H L Liu, W Dong
It appears to be a common sense to measure the crowdedness of a fluid system by the densities of the species constituting it. In the present work, we show that this ceases to be valid for confined fluids under some conditions. A quite thorough investigation is made for a hard sphere (HS) fluid adsorbed in a hard sphere matrix (a quench-annealed system) and its corresponding equilibrium binary mixture. When fluid particles are larger than matrix particles, the quench-annealed system can appear much more crowded than its corresponding equilibrium binary mixture, i...
June 21, 2017: Journal of Chemical Physics
Renjie Chen, Erik Lascaris, Jeremy C Palmer
Recent equation of state calculations [E. Lascaris, Phys. Rev. Lett. 116, 125701 (2016)] for an ionic model of silica suggest that it undergoes a density-driven, liquid-liquid phase transition (LLPT) similar to the controversial transition hypothesized to exist in deeply supercooled water. Here, we perform extensive free energy calculations to scrutinize the model's low-temperature phase behavior and confirm the existence of a first-order phase transition between two liquids with identical compositions but different densities...
June 21, 2017: Journal of Chemical Physics
Nanna Holmgaard List, Patrick Norman, Jacob Kongsted, Hans Jørgen Aagaard Jensen
We present a derivation of linear response theory within polarizable embedding starting from a rigorous quantum-mechanical treatment of a composite system. To this aim, two different subsystem decompositions (symmetric and nonsymmetric) of the linear response function are introduced and the pole structures as well as residues of the individual terms are discussed. In addition to providing a thorough justification for the descriptions used in polarizable embedding models, this theoretical analysis clarifies which form of the response function to use and highlights complications in separating out subsystem contributions to molecular properties...
June 21, 2017: Journal of Chemical Physics
Kristian Berland, Yang Jiao, Jung-Hoon Lee, Tonatiuh Rangel, Jeffrey B Neaton, Per Hyldgaard
Two hybrid van der Waals density functionals (vdW-DFs) are developed using 25% Fock exchange with (i) the consistent-exchange vdW-DF-cx functional [K. Berland and P. Hyldgaard, Phys. Rev. B 89, 035412 (2014)] and (ii) with the vdW-DF2 functional [K. Lee et al., Phys. Rev. B 82, 081101 (2010)]. The ability to describe covalent and non-covalent binding properties of molecules is assessed. For properties related to covalent binding, atomization energies (G2-1 set), molecular reaction energies (G2RC set), and ionization energies (G21IP set) are benchmarked against experimental reference values...
June 21, 2017: Journal of Chemical Physics
P Soulard, B Madebène, B Tremblay
For the first time, complexes involving carbonyl sulfide (OCS) and water molecules are studied by FTIR in solid neon. Many new absorption bands close to the known fundamental modes for the monomers give evidence for at least three (OCS)n-(H2O)m complexes, noted n:m. With the help of theoretical calculations, two isomers of the 1:1 complex are clearly identified. Concentration effects combined with a detailed vibrational analysis allow for the identification of transitions for the 1:1, 1:2, and 2:1 complexes...
June 21, 2017: Journal of Chemical Physics
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