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Infrared Spectra of the CH3NH3PbI3 Hybrid Perovskite: Signatures of Phase Transitions and of Organic Cation Dynamics
Journal of Physical Chemistry C. 2020. Vol. 124. No. 42. P. 23307–23316.
Kirill N. Boldyrev, Vasilisa E. Anikeeva, Marina N. Popova, Semenova O.
The high-resolution terahertz reflection and mid- and near-infrared transmission spectroscopic studies of CH3NH3PbI3 hybrid perovskite single crystals are performed for the temperature range from 5 to 350 K. The observation of the torsional mode of the molecular cation (at 306 cm–1) and of 12 other low-frequency modes not observed before is reported. Mode Grüneisen parameters for the strongest inorganic-cage modes are negative, which points to their interaction with a soft mode. Sharp peculiarities and the hysteresis take place in the multiphonon spectra at the phase transition from the tetragonal to the orthorhombic phase (∼160 K). Moreover, pronounced spectral changes are observed at ∼70 K; they correlate with the transition to tunneling dynamics. A spectral line splitting at this temperature is tentatively attributed to the tunneling splitting.
Chemical Papers 2026
Benzenoid hydrocarbons are structurally regular aromatic compounds, which makes them well suited for quantitative structure–property relationship (QSPR) studies. This study presents a QSPR analysis of nineteen benzenoid hydrocarbon species using degree-based topological co-indices. We developed a Python program to compute eleven degree-based topological co-indices from molecular graphs and evaluated their ability to explain variations in ...
Added: September 8, 2026
Gurina D., Fashchevsky K. A., Oparin R. D. et al., Surfaces and Interfaces 2026 Vol. 98 Article 110545
In this work, we combine experimental characterization and molecular dynamics (MD) simulations to elucidate the molecular mechanisms governing the impregnation of mefenamic acid (MFA) into nanocrystalline cellulose (NCC) aerogels. NCC aerogels were impregnated with MFA in scCO2, and low-temperature nitrogen adsorption revealed a concentration-dependent decrease in surface area, pore volume, and pore size, with an ...
Added: September 8, 2026
Budkov Y., Journal of Chemical Physics 2026 Vol. 165 No. 9 Article 094902
We derive the stress tensor of a flexible polymer solution within the Gaussian-chain self-consistent field theory (SCFT) without invoking the ground-state dominance (GSD) approximation. Starting from a covariant formulation of the single-chain partition function in a background metric, we obtain the symmetric stress tensor expressed through the full Edwards propagators. The result contains the local ...
Added: September 2, 2026
Belousov Y., Кискин М. А., Sidoruk A. et al., Australian Journal of Chemistry 2022 Vol. 75 No. 9 P. 572–580
Four new complexes [Ln(pfaa)3(H2O)2]n (Ln = Eu (1), Tb (2)) and [Ln2Cd2(pfaa)10 (phen)2(EtOH)2]·2MeCN (Ln = Eu (3), Tb (4), phen = 1,10-phenanthroline) based on pentaphorphenylacetic acid (Hpfaa) have been prepared and completely investigated. The structures of compounds 1 and 3 were studied by single crystal X-ray diffraction analysis: the isostructural complexes 1 and 2 represent ...
Added: August 26, 2026
Mazur D., Petr E. Brandyshev, Doronin S. et al., Electrochimica Acta 2026 Vol. 577 Article 149729
The electric double layer (EDL) at a single-crystal metal surface is controlled not only by the electrolyte composition and the electrode potential, but also by the atomic structure of the surface itself. This makes the Ag(hkl)/NaF interface a stringent test for continuum theories of the EDL. In the third part of our series, we examine ...
Added: August 20, 2026
Budkov Y., Kalikin N., Journal of Chemical Physics 2026 Vol. 165 Article 064506
A self-consistent statistical-mechanical theory of the Hall effect in electrolyte solutions is developed by extending the self-consistent Debye–Hückel–Onsager (SCDHO) framework to crossed electric and magnetic fields. The theory incorporates non-local ionic charge distributions via Slater-type form factors, regularizing the Coulomb interaction at short range, and accounts for dielectric friction through ion-specific coefficients, employing experimental values ...
Added: August 12, 2026
Obijiofor O., Alexander S. Novikov, New Journal of Chemistry 2026 Vol. 50 No. 33 P. 13931–13957
The rational design of coinage metal nanocarriers requires a mechanistic understanding of metal-drug binding and predictive descriptors that translate molecular interactions into design rules. Using DFT (B3LYP-D3BJ/def2-TZVP, SMD water), we systematically investigated the binding of 5-fluorouracil (5-FU) and levodopa (l-DOPA) to neutral and cationic homo- and heteronuclear dimers of Au, Ag, and Cu (Au2, Ag2, ...
Added: August 12, 2026
Voropaeva D., S. Novikova, I. Stenina et al., Solid State Ionics 2026 Vol. 445 Article 117288
Composite gel polymer electrolytes based on a perfluorinated sulfonic acid cation-exchange MF-4SC membrane
containing surface-sulfonated nanoparticles of aluminum oxide, cerium (IV) oxide, and titanium oxide (sAl2O3,
sCeO2, and sTiO2, respectively) were prepared by casting from a dispersion in N,N-dimethylformamide and
plasticized with a 1,3-dioxolane/1,2-dimethoxyethane mixture. The influence of the filler nature on ionic conductivity,
solvent uptake, activation energy, lithium ...
Added: July 30, 2026
Korogod D., Shapeev A., Ivan S. Novikov, Physical Review B: Condensed Matter and Materials Physics 2026 Vol. 114 No. 2 Article 024104
We present two models with explicit long-range electrostatics in the form of Coulomb interactions. Both models include point charges depending on their local atomic environments, and the second model also conserves a total charge of an atomic system. We combine the proposed long-range models with the local moment tensor potential (MTP) and demonstrate that they ...
Added: July 22, 2026
Moshkina E., Molokeev M., Zolotov A. et al., Journal of Alloys and Compounds 2026 Vol. 1077 Article 189412
A wide series of substitutions in a subsystem of small radii cations M = Al, Cr, Fe, Ga, Sc is possible in rare-earth borates ReM3(BO3)4 with the huntite structure. However, the existence of these compounds where M = Mn still raises doubts. The study presents a synthetic approach developed in the framework of the flux method allowing for the required ...
Added: June 29, 2026
Schneider M., Zaripov D., Dokin R. et al., Journal of Chemical Theory and Computation 2026 Vol. 22 No. 9 P. 4405–4414
Density functional theory (DFT) is the workhorse of modern reactions and materials modeling. While the exact functional remains unknown, many approximations to it have been constructed either by hand-crafting functional forms to satisfy exact constraints or by machine learning. In this work, we show how both of these approaches can be fused to build both ...
Added: June 26, 2026
Laurinavichyute V., Levin E. E., Mironkova A. A. et al., Surfaces and Interfaces 2026 Vol. 81 Article 108389
In this work we characterize mixed Mo-W acidic deposition solutions with Mo content ranging from 0 to 100 mol.% by Raman and UV–Vis spectroscopy. The obtained distribution diagram of mixed isopolyanions allows one to explain the observed change in film deposition rate with increase in Mo content. It was found that the initial decrease in ...
Added: June 24, 2026
Filippova A. V., Yurchenko N. Y., Smirnov S. A. et al., Journal of Alloys and Compounds 2026 No. 1074 Article 189162
This study investigates the effects of post-processing heat treatment at 300–500 °C on the microstructure, hardness, and tensile properties of laser powder bed fusion (PBF-LB) processed Al-bronze processed with energy densities (ED) in the range of 125–938 J/mm3. In the as-printed state, sharp needle-like α + β′ laths form at lower ED whereas with increasing ED, the β′ ...
Added: June 12, 2026
Obijiofor O., Novikov A., New Journal of Chemistry 2026 Vol. 50 No. 23 P. 9749–9768
Rational design of gold-based nanocarriers for neurotherapeutics requires atomic-scale understanding of drug-material interactions. Density functional theory calculations were performed to investigate levodopa (L-DOPA) adsorption on small gold clusters (Au2–Au4) with cationic, neutral, and anionic charges, with additional validation on a larger Au10 cluster using multiple low-energy isomers. Binding free energies (ΔGbind), charge transfer, and electronic descriptors ...
Added: June 3, 2026
Kovaleva N. N., Chvostova D., Fursova T. N. et al., Journal of Chemical Physics 2025 Vol. 163 No. 19 Article 194711
The intrinsic substitutional and antisite defects cause unintentional doping and a shift of the E-F position above the conduction band minimum in the AF topological insulator MnBi2Te4. This prevents measurements of the quantum anomalous Hall effect and the investigation of the topological Dirac states. In the present study, the Mn-Bi-Te films grown by the MBE ...
Added: February 18, 2026
Dmitriev A., Lebedev A., Kornilov V. et al., Frontiers in Physics 2025 Vol. 12 Article 1508465
Our study is based on the hypothesis that stock exchanges, being nonlinear, open and dissipative systems, are capable of self-organization to the edge of a phase transition. To empirically support the hypothesis, we find segments in hourly stock volume series for 3,000 stocks of publicly traded companies, corresponding to the time of stock exchange’s stay ...
Added: January 23, 2025
Sukhoverkhova D., Shchur L., Письма в Журнал экспериментальной и теоретической физики 2024 Т. 120 № 8 С. 644–649
In this paper, we applied a deep neural network to study the issue of knowledge transferability between statistical mechanics models. The following computer experiment was conducted. A convolutional neural network was trained to solve the problem of binary classification of snapshots of snapshots of the location of spins of the Ising model on a two-dimensional ...
Added: September 25, 2024
Kochergin D., Khaymovich I., Olga Valba et al., Physical Review B: Condensed Matter and Materials Physics 2023 Vol. 108 No. 9 Article 094203
We consider the properties of the random regular graph with node degree d perturbed by chemical potentials μk for a number of short k-cycles. We analyze both numerically and analytically the phase diagram of the model in the (μk,d) plane. The critical curve separating the homogeneous and clusterized phases is found and it is demonstrated that the clusterized phase itself generically is ...
Added: September 19, 2023
Nikita S. Komarov, Vladimir M. Shevlyuga, Loginov B. et al., Journal of Physical Chemistry C 2023 Vol. 127 No. 5 P. 2266–2273
Adsorption of molecular chlorine onto the Ag(110) surface has been studied with low-temperature scanning tunneling microscopy, low-energy electron diffraction, and density functional theory calculations (DFT). At a coverage of 1/2 ML, chlorine forms a p(2 × 1) structure, which, with a further increase in coverage, transforms into a p(3 × 1) structure consisting of dimer rows. DFT ...
Added: June 27, 2023
Chertenkov V., Burovskiy E., Shchur L., / Series "stat-mech". 2023. No. 2305:0334.
We analyze the problem of supervised learning of ferromagnetic phase transitions from the statistical physics perspective. We consider two systems in two universality classes, the two-dimensional Ising model and two-dimensional Baxter-Wu model, and perform careful finite-size analysis of the results of the supervised learning of the phases of each model. We find that the variance ...
Added: May 8, 2023
M. A. Fadeeva, L. N. Shchur, Journal of Experimental and Theoretical Physics 2022 Vol. 135 No. 6 P. 869–875
The critical behavior of a four-component Potts model on a hexagonal lattice is investigated numerically. A modified Wang–Landau method is used with controlled accuracy of estimating the density of states (DOS). The finite-dimensional analysis of the results confirms the presence of a second-order phase transition with critical exponents corresponding to the universality class of the ...
Added: February 27, 2023
Danilov V., Gaydukov R., Russian Journal of Mathematical Physics 2023 Vol. 30 No. 2 P. 165–175
In this paper, we construct and study a model of a phase transition in a system of two
phases (liquid and ice) and three media — water, a piece of ice, and some nonmeltable
solid substrate. Namely, the melting-crystallization process is considered in the problem
of water flow along a small ice irregularity (such as a frozen drop) ...
Added: December 14, 2022
Olga Valba, Gorsky A., Scientific Reports 2022 Vol. 12 No. 1 Article 5540
It is important to reveal the mechanisms of propagation in diferent cognitive networks. In this study, we discuss the k-clique percolation phenomenon as related to the free association networks including the English Small World of Words project (SWOW-EN). We compared diferent semantic networks and networks of free associations for various languages. Surprisingly, k-clique percolation for ...
Added: October 29, 2022
Фадеева М. А., Shchur L., Журнал экспериментальной и теоретической физики 2022 Т. 162 № 6 С. 909–916
The critical behavior of the four-component Potts model on a hexagonal lattice is studied numerically. The modified Wang-Landau method with the control of the density of states estimation accuracy is used. A finite-dimensional analysis of the results obtained confirms the presence of a second-order phase transition with critical exponents corresponding to the universality class of ...
Added: September 5, 2022