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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shestakov V. A., Korshunov M. M.
Заглавие : Thermodynamics of s±-to- s++ transition in iron pnictides in the vicinity of the Born limit
Колич.характеристики :8 с
Место публикации : Supercond. Sci. Technol. - 2025. - Vol. 38, Is. 5. - Ст.055002. - ISSN 09532048 (ISSN), DOI 10.1088/1361-6668/adc8dd. - ISSN 13616668 (eISSN)
Примечания : Cited References: 55
Аннотация: To study the thermodynamic properties of the disorder-induced transition between s± and s++ superconducting gap functions, we calculate the grand thermodynamic potential Ω in the normal and the superconducting states. An expression for the difference between the two, ΔΩ, is derived for a two-band model for Fe-based systems with nonmagnetic impurities. The disorder is considered in a T-matrix approximation within the multiband Eliashberg theory. In the vicinity of the Born limit near the s±-to- s++ transition, we find two solutions obtained for opposite directions of the system’s evolution with respect to the impurity scattering rate. By calculating the change in entropy ΔS and the change in the electronic specific heat ΔC from ΔΩ, we show that such a hysteresis is not due to the time-reversal symmetry breaking state, but that it instead points to the first order phase transition (PT) induced by the nonmagnetic disorder. Based on the ΔΩ calculations, a phase diagram is plotted representing the energetically favorable s± and s++ states and the transition between them. At finite temperature, a first order PT line there is limited by a critical end point. Above that point, the sharp s±→s++ transition transforms into a crossover between s± and s++ states.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vereshchagin S., Dudnikov V. A.
Заглавие : Empirical analysis of stability of An+1BnO3n+1 Ruddlesden–Popper phases using reciprocal n-values
Колич.характеристики :8 с
Место публикации : Crystals. - 2024. - Vol. 14, Is. 11. - Ст.954. - ISSN 20734352 (eISSN), DOI 10.3390/cryst14110954
Примечания : Cited References: 29. - The work was carried out within the framework of the state assignment of the Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (project FWES 2021-0013)
Аннотация: Layered An+1BnO3n+1 (n = 1…∞) Ruddlesden–Popper (RP) phases are a promising system for a variety of applications. Within the RP family, the thermodynamic properties of the phases are essentially additive with variation in the n value, but at present, there are no general approaches that would allow one to evaluate the individual stability of the RP phases and the possibility of their interconversion. The aim of this paper is to present a novel concept for performing a thermodynamic analysis of RP phases using the reciprocal values of the index n. We present an empirical equation ΔG1/n = ΔGP + B1/n + B2/n2, where ΔG1/n and ΔGP are the molar Gibbs energies of formation of the Ruddlesden–Popper (RP) phase (AO)1/nABO3 and the parent ABO3 perovskite, respectively, and n is a stoichiometry index of An+1BnO3n+1 RP phase. The correlation was validated using available thermodynamic data for the systems Sr-Ti-O, Ca-Ti-O, Sr-Zr-O, La-Ni-O, and La-Co-O. For all A-B combinations, the equation quantitatively describes the Gibbs energy of RP phase formation. Predicted values for the non-linear approximation lie within the experimental uncertainty in determining ΔG1/n. The proposed correlation was used to analyze the relative stability of the RP phases and to determine the feasibility of synthesizing new compounds.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I.
Заглавие : Thermodynamics of spin ice on an antiperovskite lattice in the cluster approximation
Колич.характеристики :5 с
Место публикации : Phys. Solid State. - 2023. - Vol. 65, Is. 7. - P.1203-1207. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2023.07.56415.63. - ISSN 10906460 (eISSN)
Примечания : Cited References: 9
Аннотация: Low-temperature thermodynamic properties of spin ice have been studied for compounds with the structure of antiperovskite containing rare-earth ions with the general chemical formula ReMeO (where Re - is a rare-earth element, Me - is a divalent metal). The calculations were carried out in the cluster approximation. The cases of undistorted and distorted ORe6 octahedron are discussed. In the case of an undistorted octahedron in the absence of an external magnetic field, the ground state of the system is infinitely degenerate. When an external magnetic field is applied, anomalies in the temperature dependences of heat capacity, entropy and magnetization are detected. In the case of a distorted octahedron and assuming that this distortion leads to the energy efficiency of two of the sixty-four configurations, it is obtained that there is a phase transition in the system of magnetic rare-earth ions.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Basova S. A., Molokeev M. S., Oreshonkov A. S., Zhernakov M. A., Khritokhin N. A., Aleksandrovsky A. S., Krylov A. S., Sal’nikova E. I., Azarapin N. O., Shelpakova N. A., Muller-Buschbaum K., Denisenko Yu. G.
Заглавие : Thermochemistry, structure, and optical properties of a new β-La2(SO4)3 polymorphic modification
Колич.характеристики :14 с
Место публикации : Inorganics. - 2023. - Vol. 11, Is. 11. - Ст.434. - ISSN 23046740 (eISSN), DOI 10.3390/inorganics11110434
Примечания : Cited References: 58. - The work was partly carried out within the framework of the Strategic Academic Leadership Program “Priority-2030” for the Kazan Federal University and the state assignment of the Kirensky Institute of PhysicsWe acknowledge Lisa-Marie Wagner (JLU Giessen) for help with X-ray powder diffractometry, and Svetlana Volkova and Irina Palamarchuk (UTMN) for help with IR- and UV-spectrometry. The use of equipment provided by the Krasnoyarsk Regional Center of Research Equipment of Federal Research Center “Krasnoyarsk Science Center SB RAS” is acknowledged
Аннотация: A new polymorphic modification of lanthanum sulfate was obtained by thermal dehydration of the respective nonahydrate. According to powder X-ray diffraction, it was established that β-La2(SO4)3 crystallized in the C2/c space group of the monoclinic system with the KTh2(PO4)3 structure type (a = 17.6923(9), b = 6.9102(4), c = 8.3990(5) Å, β = 100.321(3)°, and V = 1010.22(9) Å3). Temperature dependency studies of the unit cell parameters indicated almost zero expansion along the a direction in the temperature range of 300–450 K. Presumably, this occurred due to stretching of the [LaO9]n chains along the c direction, which occurred without a significant alteration in the layer thickness over the a direction. A systematic study of the formation and destruction processes of the lanthanum sulfates under heating was carried out. In particular, the decisive impact of the chemical composition and formation energy of compounds on the thermodynamic and kinetic parameters of the processes was established. DFT calculations showed β-La2(SO4)3 to be a dielectric material with a bandgap of more than 6.4 eV. The processing of β-La2(SO4)3 with the Kubelka–Munk function exhibited low values below 6.4 eV, which indicated a fundamental absorption edge above this energy that was consistent with LDA calculations. The Raman and infrared measurements of β-La2(SO4)3 were in accordance with the calculated spectra, indicating that the obtained crystal parameters represented a reliable structure.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Pavlovskii M. S.
Заглавие : Thermodynamics of spin ice in staggered and direct (along the [111] axis) fields in the cluster approximation
Коллективы : Russian Foundation for Basic Research; Government of the Krasnoyarsk Territory; Krasnoyarsk Territory Foundation for Supporting the Scientific and Research Activity [16-42-243039]
Место публикации : J. Exp. Theor. Phys. - 2017. - Vol. 124, Is. 2. - P.295-303. - ISSN 1063-7761, DOI 10.1134/S1063776117020182. - ISSN 1090-6509(eISSN)
Примечания : Cited References:15. - This work was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, and the Krasnoyarsk Territory Foundation for Supporting the Scientific and Research Activity (project no. 16-42-243039).
Предметные рубрики: ENTROPY
HEAT
Аннотация: We have analyzed the low-temperature thermodynamic properties of spin ice in the staggered and direct (acting along the [111] axis) fields for rare-earth oxides with the chalcolamprite structure and general formula Re23+Me24+O72- . Calculations have been performed in the cluster approximation. The results have been compared with experimental temperature dependences of heat capacity and entropy for Dy2Ti2O7 compound for different values of the external field in the [111] direction. The experimental data and calculated results have also been compared for the Pr2Ru2O7 compound with the antiferromagnetic ordering of magnetic moments of ruthenium ions, which gives rise to the staggered field acting on the system of rare-earth ions. The calculated temperature dependences of heat capacity and entropy are in good agreement with experimental data.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : Effect of intersite repulsion on the correlation functions and thermodynamics of an Ising chain with annealed magnetic disorder
Место публикации : Bull. Russ. Acad. Sci. Phys. - 2016. - Vol. 80, Is. 11. - P.1335-1337. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816110290
Примечания : Cited References: 6. - This work was supported by the Russian Foundation for Basic Research, project nos. 13-02-00073, 14-02-31237, and 15-42-04372.
Ключевые слова (''Своб.индексиров.''): chains--magnetic susceptibility--temperature distribution--thermodynamics--transfer matrix method--correlation function--equilibrium behavior--equilibrium distributions--non-magnetic impurities--quantum phase transitions--repulsion parameter--temperature dependence--transfer matrix technique--phase transitions
Аннотация: An exact solution for a model describing the equilibrium behavior of an ensemble of Ising chains with nonmagnetic intersite repulsion of nearest neighbors and an equilibrium distribution of nonmagnetic impurities is obtained using the transfer matrix technique. The possibility of exciting quantum phase transitions using the intersite repulsion parameter in a system is demonstrated. Proximity to the critical points of these transitions has a substantial effect on the temperature dependence of a system’s magnetic susceptibility. © 2016, Allerton Press, Inc.
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7.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Sidorov K. A., Tikhonov N. V., Ovchinnikov S. G.
Заглавие : Exact solution for the thermodynamics of the one-dimensional Hubbard model with infinite repulsion in a magnetic field
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016): abstracts/ ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk: KIP RAS SB, 2016. - Ст.P1.43. - P.104. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Примечания : References: 4
Ключевые слова (''Своб.индексиров.''): hubbard model--magnetic field--infinite repulsion--thermodynamics--exact solution
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8.

Вид документа : Статья из сборника (выпуск продолж. издания)
Шифр издания :
Автор(ы) : Mironov V. L., Molostov I. P., Scherbinin V. V.
Заглавие : Dielectric model of a mineral arctic soil thawed and frozen at 0.05-15 GHz
Коллективы : International Siberian Conference on Control and Communications
Место публикации : Int. Sib. Conf. on Control and Communicat. (SIBCON 2015): Proceedings: IEEE-Institute Electrical and Electronics Engineers, 2015. - P.1-7. - , DOI 10.1109/SIBCON.2015.7147146
Ключевые слова (''Своб.индексиров.''): arctic regions--dielectric model--dielectric relaxation--remote sensing--soil--temperature dependence--dielectric relaxation--moisture--remote sensing--soil moisture--soils--temperature--temperature distribution--thawing--thermodynamics--active and passive remote sensing--arctic regions--complex dielectric constant--dielectric modeling--soil dielectric constant--spectroscopic parameters--temperature dependence--thermodynamics parameters--soil surveys
Аннотация: The dielectric model for an arctic soil both thawed and frozen has been developed. The model is based on the soil dielectric measurements carried out in the ranges of gravimetric moisture from 0.01 to 0.43 g/g, dry soil density from 1.25 to 1.83 g/cm3, and temperature from 25 to -30°C (cooling run), in the frequency range 0.05-15 GHz. To fit the results of measurements of the soil complex dielectric constant as a function of soil moisture and wave frequency, the refractive mixing dielectric model in conjunction with the Debye multi-relaxation equations were applied. As a result, the spectroscopic parameters of dielectric relaxations for the bound, transient bound, and unbound soil water components were derived, being further complimented with the thermodynamics parameters to ensure a complete set of parameters of the temperature dependent multi-relaxation spectroscopic dielectric model for moist soils proposed. To calculate complex dielectric constant of soil, the following input variables have to be assigned: 1) density of dry soil, 2) gravimetric moisture, 3) wave frequency, and 4) temperature. The error of the dielectric model was evaluated in terms of RMSE, yielding the values RMSE of 0.53 and 0.43 for the soil dielectric constant and loss factor, respectively. These values appeared to be in the order of the dielectric measurement error itself. The dielectric model suggested can be applied in the active and passive remote sensing techniques in microwave to develop algorithms for retrieving soil moisture and freeze/thaw state of the topsoil in the Arctic regions. © 2015 IEEE.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sidorov K. A., Tikhonov N. V., Ovchinnikov S. G.
Заглавие : Exact solution for the thermodynamics of the one-dimensional Hubbard model with infinite repulsion in a magnetic field
Коллективы : Russian Federation Ministry of Education and Science [SFU 2014 GF-2]; Presidium of the Russian Academy of Sciences [20.7]; Program for Supporting Leading Scientific Schools [NSh-1044.2012.2]; Russian Foundation [10-02-00251]; Siberian Federal University [NF-11]
Место публикации : Theor. Math. Phys. - 2014. - Vol. 180, Is. 1. - P.835-849. - ISSN 0040-5779, DOI 10.1007/s11232-014-0183-9. - ISSN 1573-9333
Примечания : Cited References: 8. - This work was supported in part by the Russian Federation Ministry of Education and Science (State Order SFU 2014 GF-2), the Presidium of the Russian Academy of Sciences (Program No. 20.7), the Program for Supporting Leading Scientific Schools (Grant No. NSh-1044.2012.2), the Russian Foundation for Basic Research (Grant No. 10-02-00251), and the Siberian Federal University (Internal Grant No. NF-11).
Предметные рубрики: FINITE TEMPERATURES
Ключевые слова (''Своб.индексиров.''): hubbard model--magnetic field--infinite repulsion--thermodynamics--exact solution
Аннотация: We demonstrate that in the limit of infinite repulsion in a magnetic field, the canonical partition function of the one-dimensional Hubbard model in the nearest-neighbor approximation factors into the product of partition functions of holons and spinons, which can be calculated exactly. We thus obtain exact numerical dependences of the free energy, entropy, internal energy, specific heat, chemical potential, and magnetic susceptibility on the hole concentration, temperature, and magnetic field induction.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Sidorov K. A., Shneyder E. I.
Заглавие : Anomalous thermodynamics of the doped Mott-Hubbard insulators
Место публикации : Phys. Solid State. - 2011. - Vol. 53, Is. 2. - P299-302. - ISSN 1063-7834, DOI 10.1134/S1063783411020247
Примечания : Cited References: 6. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00127), the Branch of the Physical Sciences of the Russian Academy of Sciences (program nos. 2 and 3), grant no. MK-1683.2010.2, and by the Federal Target Program "Personnel" (project NK-589 P).
Предметные рубрики: T-J MODEL
SPECTRUM
Аннотация: The concentration dependence of the entropy of doped Mott-Hubbard insulators has been considered within the t-J model. It has been shown that a change in the type and statistics of charge carriers as compared to the Fermi gas leads to a radical change in the entropy s, in particular, to the giant growth of the entropy upon doping. The quantity a,s/a,x a parts per thousand k (B) is approximately consistent with the experimental data for HTSC cuprates in the pseudogap phase.
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