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Physical Chemistry Chemical Physics: PCCP

Ryota Tamate, Takeshi Ueki, Mitsuhiro Shibayama, Ryo Yoshida
We developed a novel type of block copolymer, named the self-oscillating block copolymer, which exhibits autonomous assembly and disassembly driven by the dissipative structures formed by the oscillatory Belousov-Zhabotinsky (BZ) reaction. In a catalyst-free BZ solution, this polymer undergoes autonomous structural changes following the periodic redox changes of a metal catalyst incorporated into the polymer side chain. However, until now, a detailed study of the relationship between the dynamic structural changes and polymer solution conditions has not been conducted...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Giuseppe Cassone, Fabrizio Creazzo, Paolo V Giaquinta, Jiri Sponer, Franz Saija
We report on a series of ab initio molecular dynamics investigations on LiCl, NaCl, and KCl aqueous solutions under the effect of static electric fields. We have found that although in low-to-moderate field intensity regimes the well-known sequence of cationic mobilities μ(K(+)) > μ(Na(+)) > μ(Li(+)) (i.e., the bigger the cation the higher the mobility) is recovered, from intense field strengths this intuitive rule is no longer verified. In fact, field-induced water molecular dissociations lead to more complex phenomena regulating the standard migration properties of the simplest monovalent cations...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Taylor R Juran, Manuel Smeu
Hybrid density functional theory (DFT) is used to study the Chevrel phase Mo6X8 (X = S, Se, Te) as a promising cathode material intercalated with various metal ions (M = Li, Na, Be, Mg, Ca, Sr, Ba, Zn, Al). Electronic properties and voltages are calculated for each case. Ca ions are predicted to produce a voltage output ranging from 1.8-2.1 V, comparable to the voltage calculated for Li ions while providing two electrons per transferred ion. The highest voltage is determined to result when the chalcogen X in Mo6X8 is S, over Se or Te...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Goar Sánchez-Sanz, Cristina Trujillo, Ibon Alkorta, José Elguero
A theoretical study of [X.X'.X'']phosphatrane:Lewis acid complexes has been carried out in order to analyze how the in:out and out:out conformations can be modulated by the interaction with Lewis acids (LA). It has been found that in:out structures are more stable in larger systems i.e. in [4.4.3]:LA and [4.4.4]:LA than in [3.3.3]:LA and [4.3.3]:LA. The results obtained for the relative energies in conjunction with electron density properties showed that upon complexation, in:out conformers become more stable with the increasing acidity of the corresponding Lewis acid...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
I Zakai, M E Varner, R B Gerber
Molecular dynamics simulations using directly ab initio potentials are carried out for the ionically bonded clusters [(Cl(-))(H3O(+))]2 and [(F(-))(H3O(+))]4 to explore their transitions to the hydrogen-bonded [(HCl)(H2O)]2 and [(HF)(H2O)]4 structures during the first picosecond of simulation. Both the ionic and the H-bonded structures that are formed are highly symmetric. It is found that proton transfers are concerted in all trajectories for [(Cl(-))(H3O(+))]2. For [(F(-))(H3O(+))]4, the fully concerted mechanism is dominant but partially concerted transfers of two or three protons at the same time also occur...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Jinfeng Liu, Xiao He
Accurate prediction of physicochemical properties of ionic liquids (ILs) is of great significance to understand and design novel ILs with unique properties. This study employed the electrostatically embedded generalized molecular fractionation (EE-GMF) method for accurate energy calculation of IL clusters. The accuracy and efficiency of the EE-GMF method are systematically assessed at different ab initio levels (including HF, DFT and MP2) with diverse basis sets. With the fixed charge model for the embedding field, the deviations of the EE-GMF approach from conventional full system calculations are within 2...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Gopal Datt, Chetan Kotabage, A C Abhyankar
The effect of cationic disorder and particle morphology on the ferromagnetic resonance (FMR) of NiCoFe2O4 nanoparticles (NPs) and the electromagnetic shielding effectiveness of flexible composites (wherein the nanoparticles are used as fillers) has been presented. Upon annealing at 1000 °C, spherical, ∼25 nm, single crystalline (as-prepared) NPs are transformed into octahedral, ∼200 nm, polycrystalline (annealed) NPs and change the cationic distribution significantly. The effect of shape, size and cationic distribution on the resonance properties has been discussed using the randomly-oriented anisotropic-axis model...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Diddo Diddens, Volker Lesch, Andreas Heuer, Jens Smiatek
Low concentrated aqueous ionic liquids (ILs) and their influence on protein structures have attracted a lot of interest over the last few years. This can be mostly attributed to the fact that aqueous ILs, depending on the ion species involved, can be used as protein protectants or protein denaturants. Atomistic molecular dynamics (MD) simulations are performed in order to study the influence of different aprotic ILs on the properties of a short hairpin peptide. Our results reveal distinct binding and denaturation effects for 1-ethyl-3-methylimidazolium (EMIM) in combination with different anions, namely, chloride (CL), tetrafluoroborate (BF4) and acetate (ACE)...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
C Paduani, Andrew M Rappe
We study with scalar relativistic density functional theory (DFT) calculations the effect of changes in the ionicity of the bonding mechanism and charge donation on the structure and electronic properties of new lead halide perovskites which show promising performance in optoelectronic applications as long-wave infrared detectors and thermoelectrics. Our results provide evidence that the band gap of these compounds can be tuned upon the introduction of appropriate superalkali moieties at the cationic A-sites in the CsPbI3-type structure...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Yang Shen, Kyuichi Yasui, Tong Zhu, Muthupandian Ashokkumar
A new model of single cavitation bubble dynamics has been developed to include the effect of bulk liquid viscosity in addition to the effects of evaporation/condensation of water vapor, thermal conduction and the compressibility of a liquid. In this study, the liquid viscosity is divided into two parts: viscosity at the bubble interface (μ') and viscosity of the bulk liquid (μ). A set of numerical calculations with and without μ has been completed under different viscosities (0.001-0.014 Pa s) to quantitatively analyze the effect of μ on single cavitation bubble dynamics...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Duy Khanh Nguyen, Yu-Tsung Lin, Shih-Yang Lin, Yu-Huang Chiu, Ngoc Thanh Thuy Tran, Ming Fa-Lin
The feature-rich electronic and magnetic properties of fluorine-doped graphene nanoribbons are investigated by the first-principles calculations. They arise from the cooperative or competitive relations among the significant chemical bonds, finite-size quantum confinement and edge structure. There exist C-C, C-F, and F-F bonds with multi-orbital hybridizations. Fluorine adatoms can create p-type metals or concentration- and distribution-dependent semiconductors, depending on whether the π bonding is seriously suppressed by the top-site chemical bonding...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Aamir Shafique, Abdus Samad, Young-Han Shin
Using density functional theory, we systematically investigate the lattice thermal conductivity and carrier mobility of monolayer SnX2 (X = S, Se). The room-temperature ultra low lattice thermal conductivities found in monolayer SnS2 (6.41 W m(-1) K(-1)) and SnSe2 (3.82 W m(-1) K(-1)) are attributed to the low phonon velocity, low Debye temperature, weak bonding interactions, and strong anharmonicity in monolayer SnX2. The predicted values of lattice thermal conductivity are lower than those of other two-dimensional materials such as stanene, phosphorene, monolayer MoS2, and bulk SnX2...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
I G Grosu, M I Rednic, M Miclăuş, I Grosu, A Bende
The nature of intermolecular interactions in different molecular crystal configurations formed by pyridinium cations, chloride or bromide anions as well as β-hexachlorocyclohexane (β-HCH) molecules has been investigated using high level ab initio quantum chemistry methods. Several molecular subsystems taken from the crystal unit cell were considered and their supramolecular energy stability was analyzed in detail using high level density-fitting local electron correlation (DF-LMP2 and DF-LCCSD(T)) methods together with the aug-cc-pVTZ basis set...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
Jie Su, Liping Feng, Siyang Liu, Zhengtang Liu
Using first-principles calculations within density functional theory, vacancies in the BN buffer layer have been predicted to improve the Schottky barrier of the metal-MoS2 interface without deteriorating the intrinsic properties of the MoS2 layer. Here, the effects of concentrations, sizes and types of vacancies on the contact properties of metal/BN-MoS2 sandwich interfaces are comparatively studied. The results show that vacancies in the BN buffer layer not only don't deteriorate the charge scatterings and electronic properties of the MoS2 layer at the metal/BN-MoS2 interface, but also improve the charge density and contact resistance between the metal surface and the BN layer...
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
D Egorov, R Hoekstra, T Schlathölter
The ionization of gas-phase protonated peptides and proteins can induce molecular responses ranging from purely non-dissociative ionization to extensive multifragmentation of the system. In the case of soft X-ray photoionization, a monotonic transition between both regimes occurs in the mass range between 0.5 and 10 kDa. Despite the localized nature of the photoabsorption, excitation energy equilibrates before fragmentation sets in and the transition reflects the increase of the heat capacity with protein size...
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
Daniel T W Toolan, Kevin Adlington, Anna Isakova, Alexis Kalamiotis, Parvaneh Mokarian-Tabari, Georgios Dimitrakis, Christopher Dodds, Thomas Arnold, Nick J Terrill, Wim Bras, Daniel Hermida Merino, Paul D Topham, Derek J Irvine, Jonathan R Howse
Microwave annealing has emerged as an alternative to traditional thermal annealing approaches for optimising block copolymer self-assembly. A novel sample environment enabling small angle X-ray scattering to be performed in situ during microwave annealing is demonstrated, which has enabled, for the first time, the direct study of the effects of microwave annealing upon the self-assembly behavior of a model, commercial triblock copolymer system [polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene]...
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
Yoshihiro Matsumura, Shuichi Hiraoka, Hirofumi Sato
Herein, the self-assembly process of an octahedron-shaped coordination capsule was analyzed based on a master equation approach using a reaction network model. This model was found to adequately reproduce the overall experimentally observed time evolutions and enabled us to trace the real-time evolution of transient intermediates, ranging from milli-second to hours. The time evolution of the distribution of individual intermediates species was obtained; a few linear-oligomers located near the reactant were produced at first, followed by an explosive increase in several types of intermediates...
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
Sadra Kashefolgheta, Ana Vila Verde
We present a set of Lennard-Jones parameters for classical, all-atom models of acetate and various alkylated and non-alkylated forms of sulfate, sulfonate and phosphate ions, optimized to reproduce their interactions with water and with the physiologically relevant sodium, ammonium and methylammonium cations. The parameters are internally consistent and are fully compatible with the Generalized Amber Force Field (GAFF), the AMBER force field for proteins, the accompanying TIP3P water model and the sodium model of Joung and Cheatham...
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
Raúl Guerrero-Avilés, Walter Orellana
The energetics and diffusion of water molecules and hydrated ions (Na(+), Cl(-)) passing through nanopores in graphene are addressed by dispersion-corrected density functional theory calculations and ab initio molecular dynamics (MD) simulations. Pores of about 0.8 nm in diameter with different pore-edge passivations, with (H) and (O, H) atoms, were considered. Our MD simulations show a water flux through the hydroxylated pores of about one H2O molecule every three picoseconds, in close agreement with recent experiments that estimated a water flux of three molecules per picosecond through pores of ∼1 nm...
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
Zhanning Liu, Chenxi Liu, Qiang Li, Jun Chen, Xianran Xing
Two nonporous coordination polymers were found to possess large anisotropic thermal expansion, which was derived from the flexible structures. A "spring-like" thermal motion was proposed to illustrate the mechanism. Compound Cd(eim)2 (eim = 2-ethylimidazole) possesses large linear and reversible thermal expansion properties and the emission intensity shows a linear decrease with temperature, making it a candidate for thermo-responsive materials.
July 21, 2017: Physical Chemistry Chemical Physics: PCCP
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