Heat Capacity Curves Research Articles

Schottky Anomaly of the Kalb-Ramond-de Sitter Spacetime

In the theory of gravity, the spontaneous breaking of Lorentz symmetry due to the non-minimal coupling between the Kalb-Ramond field and Einstein gravity results in the existence of exactly static and spherically symmetric black hole solutions related to the Lorentz violating parameter. Based on the consideration of the interaction between the black hole and cosmological horizons, this paper studies the thermodynamic properties of Kalb-Ramond-de Sitter (KR-dS) spacetime. The Smarr relation expressed by equivalent thermodynamic quantities is found, and it is proved that the equivalent thermodynamic quantities of the KR-dS spacetime satisfy the universal Euler's theorem. It is discovered that the heat capacity of the KR-dS spacetime with respect to the ratio of the two horizons and the variation curve of the heat capacity with effective temperature possess the characteristics of Schottky specific heat. Moreover, the black hole and the cosmological horizon in the equivalent thermodynamic system are regarded as two different energy levels, and the heat capacity of the KR-dS spacetime is discussed using the general form given by the ordinary two-level system. It is found that the heat capacity of KR-dS spacetime described by equivalent thermodynamic quantities not only conforms to the characteristics of Schottky specific heat but also is consistent with the heat capacity of the ordinary two-level system. This result reflects that when the cosmological constant and the charged carried in the KR-dS spacetime remain unchanged, the heat capacity of the system can be represented by a universal two-level system. By comparing the maximum value of the heat capacity curves, the number of microscopic particles between the two horizons can be estimated, which reflects the quantum properties of the KR-dS spacetime. These studies will open a new perspective to probe the thermodynamics of black holes.

Predicting the volumetric heat capacity of freezing soils using the soil freezing characteristic curve

The heat capacity during the freezing process is a vital hydrothermal parameter. It is difficult to experimentally measure the heat capacity of freezing soils. Therefore, in this study, we proposed a new method to estimate the volumetric heat capacity based on the combination of the weighted arithmetic mean model for volumetric heat capacity and soil freezing characteristic curve (SFCC) estimation model. Five specific heat capacity models for solid particle and six SFCC estimation models were introduced. It can be concluded that the six SFCC-based volumetric heat capacity models with specific heat capacity of solid particle = 0.725 MJMg-1K−1 exhibited the best performance. Among the six SFCC-based volumetric heat capacity models, the Kong et al-based volumetric heat capacity model has the best performance in predicting the volumetric heat capacity. The predicted SFCC-based volumetric heat capacity model is easy to use and can be applied to mimic the variation of volumetric heat capacity with subzero temperature.

Study on the magnetothermal properties of the [formula omitted] series of compounds

In this work, we developed a theoretical model Hamiltonian, in the mean field approximation, to describe the magnetic and magnetocaloric behavior of the series of compounds Dy1-xTbxAl2(x=0.00,0.15,0.25,0.30,0.35,0.40 and 0.75). We adjusted the exchange parameters λDyDy,λTbTb, and λDyTb to obtain the spin reorientation temperatures TSR and the critical temperature TC for each compound in the series. The results obtained by the Hamiltonian model agree satisfactorily with the experimental results. The heat capacity curves with and without an applied magnetic field, adiabatic temperature variation and isothermal entropy variation were modeled and compared with the experimental data. As the experimental results show, our model was also able to reproduce the change in the spin reorientation process: a first order spin reorientation transition appears for concentrations x = 0.15, 0.25, 0.30, 0.35, and no spin reorientation transitions after x = 0.40.

Pairing phase transition in the odd-A nuclei: identification and classification* *Supported by the National Natural Science Foundation of China ( 11775099 ) and the Jiangnan University Basic Research Program (JUSRP202406002)

Research on the pairing phase transition in the odd-A nucleus is based on a sophisticated blend of the covariant density functional theory and the shell-model-like approach. It has been observed that variations in thermodynamic quantities at the critical temperature do not exclusively align with pairing phase transitions. The presence of an S-shaped heat capacity curve, often interpreted as an indicator of such transitions, does not offer a definitive confirmation. Additional factors, including the blocking effect, can modify the heat capacity curve and impede the transition process. The pairing phase transition in , which occurs approximately from 0.7 to 1.0 MeV, is unequivocally characterized as a first-order transition. Furthermore, the analysis of the impact of varying strengths of pairing correlations on these transitions reveals a nonlinear relationship, thereby adding complexity to the transition dynamics.

Magnetic exchange interactions and non-Debye relaxation in spin-3/2 frustrated Kagomé magnet Co3V2O8

We report the experimental determination of the magnetic exchange parameter ( J/kB = 2.88 ± 0.02 K) for the Spin-3/2 ferromagnetic (FM) Kagomé lattice system: Co3V2O8 using the temperature dependence of dc-magnetic susceptibility χ(T) data by employing the fundamental Heisenberg linear chain model. Our results are quite consistent with the theoretically reported nearest neighbor dominant FM exchange coupling strength Jex−NN∼ 2.45 K. Five different magnetic phase transitions (6.2–11.2 K) and spin-flip transitions (9.6–7.7 kOe) have been probed using the ∂ ( χT )/ ∂T vs. T, heat capacity (CP -T) and differential isothermal magnetization curves. Among such sequence of transitions, the prominent ones being incommensurate antiferromagnetic (AFM) state at 11.2 K, commensurate AFM state at 8.8 K, and commensurate FM state across 6.2 K. All the successive magnetic phase transitions have been mapped onto a single H-T plane through which one can easily distinguish the above-mentioned different phases. The magnetic contribution of the CP -T near TN (11.2 K) has been analyzed using the power-law expression CM = A|T — TN|−α resulting in the critical exponent α = 0.18 ± 0.01 (0.15 ± 0.003) for T < TN (T > TN ), respectively for the Co3V2O8. It is interesting to note that non-Debye type dipole relaxation is quite prominent in Co3V2O8 and was evident from the Kohlrausch–Williams–Watts analysis of complex modulus and impedance spectra (0 ⩽β⩽ 1). Mott’s variable-range hopping of charge carriers process is evident through the resistivity analysis ( ρac -T −1/4 ) in the temperature range 275 ∘C–350 ∘C. Moreover, the frequency-dependent analysis of σac (ω) follows Jonscher’s power law yielding two distinct activation energies ( Ea∼ 0.37 and 2.29 eV) between the temperature range 39 ∘C–99 ∘C and 240 ∘C–321 ∘C.

Experimental investigation of thermophysical properties of propylene glycol based secondary fluids for ground source heat pumps and indirect refrigeration systems

More than 1.7 million ground source heat pumps are currently in operation in the European Union and a large majority of systems is using propylene glycol as secondary fluid. In this study the thermophysical properties of propylene glycol solutions with specific freezing points between −5 and −50 °C are investigated at low temperatures of interest for refrigeration and heat pump applications. The experimentally determined data are compared to a large number of data from the literature. It has been found that the freezing point results for all concentrations were in very good agreement with both Melinder (2010) and ASHRAE (2021) data. Moreover, the literature data and present study for concentrations above 40 wt-% have different density curve slopes compared to ASHRAE data. The viscosity results for concentrations below 40 wt-% were up to 21.5 % higher than ASHRAE data and the viscosity results for solutions with concentrations above 40 wt-% were lower by up to 9.7 %. The thermal conductivity results for concentrations above 40 wt-% were 10 % higher than ASHRAE (2021) data. The experimental specific heat capacity curves and other studies do not have the same linear trend as Melinder (2010) and ASHRAE (2021) data. This difference indicates that currently available ASHRAE data have been indirectly computed from thermal conductivity data or that they have not been fully experimentally validated. Finally, more studies are required to investigate concentrations below 25 wt-% to identify solutions with higher specific heat capacity than water that could be of interest for specific applications.

A Theoretical Study of the Phase Transition in the Binding of DNA with Mithramycin

In the present investigation, we report the theoretical analysis of mithramycin A (MTA) and mithramycin SK (MSK) binding to salmon testes DNA utilizing a modified Zimm and Bragg theory to explain the melting behavior and heat capacity of the DNA before and after drug binding. The sensitivity parameter and half width were employed in tandem to analyze the melting transition’s sharpness. According to the results, a number of metrics, including transition profile, sharpness of transition, heat capacity curve, and half widths, were in good agreement with the experimental observations. The development of novel medications would be made easier by having a better understanding of the molecular interactions between pharmaceuticals and DNA. This theoretical investigation brings us a step closer to the objective of comprehending the stability of nucleic acid interactions with medications and has potential applications in the biomedical industry.

Pd8 Cluster: Too Small to Melt? A BOMD Study.

The question of whether a solid-liquid phase transition occurs in small clusters poses a fundamental challenge. In this study, we attempt to elucidate this phenomenon through a thorough examination of the thermal behavior and structural stability of Pd8 clusters employing ab initio simulations. Initially, a systematic global search is carried out to identify the various isomers of the Pd8 cluster. This is accomplished by employing an ab initio basin-hopping algorithm and using the PBE/SDD scheme integrated in the Gaussian code. The resulting isomers are further refined through reoptimization using the deMon2k package. To ensure the structural firmness of the lowest-energy isomer, we calculated normal modes. The structural stability as a function of temperature is analyzed through the Born-Oppenheimer molecular dynamics (BOMD) approach. Multiple BOMD trajectories at distinct simulated temperatures are examined with data clustering analysis to determine cluster isomers. This analysis establishes a connection between the potential energy landscape and the simulated temperature. To address the question of cluster melting, canonical parallel-tempering BOMD runs are performed and analyzed with the multiple-histogram method. A broad maximum in the heat capacity curve indicates a melting transition between 500 and 600 K. To further examine this transition, the mean-squared displacement and the pair-distance distribution function are calculated. The results of these calculations confirm the existence of a solid-liquid phase transition, as indicated by the heat capacity curve.

Coexistence of two lamellar populations in poly(ethylene vanillate) reorganized upon heating

The structural evolution of poly(ethylene vanillate) (PEV) crystals, after isothermal crystallization at Tc = 180 °C, was explored by synchrotron wide-angle and small-angle X-ray scattering (WAXS and SAXS) measurements. The WAXS/SAXS analyses proved that an additional more perfect crystal population starts to grow exactly in correspondence of the exotherm displayed by the specific heat capacity curve. The study ascertained that two different reorganization/recrystallization mechanisms occur upon heating: the more perfect crystals originate from a recrystallization process, whereas the original crystals undergo small and progressive perfection maybe without previous complete fusion. Deconvolution of the double Lorentz-corrected SAXS profiles was performed to calculate the temperature evolution of the lamellar thickness for the original and additional crystal populations. The two crystal populations appear to differ substantially in the temperature evolution of the lamellar and amorphous thicknesses. Hypotheses on the relative location of the two different crystal stacks as well as on the possible thermodynamic reason that triggers the formation of the more perfect crystal population have been formulated.

Physical origin of the second damping peak in ionomers as traced by enthalpy relaxation

Ionomers possess two loss factor peaks, thus providing a possibility for the fabrication of novel damping materials. Eisenberg et al. assigned the second damping peak to the glass transition of restricted regions in the ionic cluster. However, the ordinary heat flow curves showed only one glass transition corresponding to the first loss factor peak. Moreover, the conventional view by multiplet/cluster model has been questioned by Simmons due to their different conclusions on the size of restricted regions (Macromolecules 2015, 48, 2313−2323). Meanwhile, we found that the storage modulus of the second damping peak was right in the modulus range of the Rouse relaxation mode. In view of these confusions, enthalpy relaxation characteristics were investigated to clarify the nature of the second loss factor peak. It was found that all the ionomers possessed anomalous enthalpy hysteresis due to the existence of two different but partly coupled glass transitions, while Rouse motion did not cause anomalous enthalpy hysteresis. Furthermore, the heat capacity curves after physical aging clearly showed two glass transition behaviors. These experimental evidences confirmed that the second loss factor peak originated from the glass transition in cluster rather than Rouse relaxation, thus further validating the view by multiplet/cluster model.

Effects of electron–phonon coupling and Rashba spin–orbit interaction on thermodynamic and magnetic properties of quantum dots

The thermodynamic and magnetic properties of quantum-dot structures subjected to an applied magnetic field were studied, including the longitudinal optical–phonon interaction and the Rashba spin–orbit effect. The Schrödinger equation was solved to determine the energy levels. The partition function was evaluated by summing the accessible energy levels and was then utilized to calculate the thermomagnetic functions. In this paper, we present magnetic properties by considering three interacting polarons. Our results indicated that at B=0T, the susceptibility exhibits diamagnetic behavior for all values of the Rashba spin–orbit parameter. However, the magnetic susceptibility increases with an applied magnetic field, and the system exhibits paramagnetic behavior under moderate magnetic fields. However, in situations with and without the polaron effect, the susceptibility is saturated at 0(meV/T2) under large magnetic fields. In this study, we showed that the Rashba spin–orbit interaction (SOI) strengthens the cutoff magnetic field Bc (the B value at which the magnetic nature of the dot changes from diamagnetic to paramagnetic). Rashba SOIs reduce the mean energy of the system, including polaronic interactions. Under the polaron effect, the heat capacity curve shifts to lower temperatures. A quantitative description of the magnetocaloric effect (ΔS) as a function of the Wigner and Rashba spin–orbit parameters is presented.

Ab initio insight into the physical properties of MgXH3 (X = Co, Cu, Ni) lead-free perovskite for hydrogen storage application.

Renewable energy systems are vital for a sustainable future, where solid-state hydrogen storage can play a crucial role. Perovskite hydride materials have attracted the scientific community for hydrogen storage applications. The current work focuses on the theoretical study using density functional theory (DFT) to evaluate the characteristics of MgXH3 (X = Co, Cu, Ni) hydrides. The structural, vibrational, electronic, mechanical, thermodynamic, and hydrogen storage properties of these hydrides were investigated. The equilibrium lattice parameters were calculated using the Birch-Murnaghan equation of state-to-energy volume curves. The elastic constants (Cij) and relevant parameters, such as Born criteria, were calculated to confirm the mechanical stability of the hydrides. The Cauchy pressure (Cp) revealed brittle or ductile behavior. The outcomes of the Pugh ratio, Poisson ratio, and anisotropy were also calculated and discussed. The absence of negative lattice vibrational frequencies in phonon dispersion confirmed the lattice's dynamic stability. The heat capacity curves of thermodynamic properties revealed that hydrides can conduct thermal energy. The metallic character and ample interatomic distances of hydrides were confirmed by the band structure and population analysis, which confirmed that hydrides can conduct electrical energy and adsorb hydrogen. The density of state (DOS) and partial DOS unveiled the role of specific atoms in the DOS of the crystal. The calculated gravimetric hydrogen storage capacity of MgCoH3, MgCuH3, and MgNiH3 hydrides was 3.64, 3.32, and 3.49wt%, respectively. Our results provide a deeper understanding of its potential for hydrogen storage applications through a detailed analysis of MgXH3 (X = Co, Cu, Ni) perovskite hydride material.

An analytic and complete equation of state for condensed phase materials

Analytic equations of state (EOS) are intended to reproduce theoretical and experimental data in a single phase portion of the thermodynamic space. We devise a complete and thermodynamically consistent model with four distinct features: (1) a reference isotherm that remains thermodynamically stable, (2) a flexible specific heat model based on a fourth-order rational polynomial, (3) a Grüneisen parameter that depends on specific volume and temperature, and (4) pressure and internal energy functions that can be inverted analytically in temperature. The model aims to improve the accuracy of existing equations of state while remaining computationally efficient. To demonstrate its features, we include calibrations for single-crystal pentaerythritol tetranitrate (PETN), liquid nitromethane (NM), and hexagonal close-packed beryllium (Be) metal. The parameter optimization uses the specific heat capacity, Grüneisen parameter, and static compression curves obtained from density functional theory for the crystalline solids and molecular dynamics simulations for liquid NM. We also present a velocity autocorrelation function that yields accurate phonon densities of states for the EOS calibration from the molecular dynamics trajectories. Each of the three calibrations is constrained to enforce the ambient state from experimental measurements and validated against experimental Hugoniot data from multiple sources. We also include one-dimensional hydrodynamic simulations of the isentropic compression experiments for beryllium conducted at the Z facility.

Assessment of phase equilibria and thermodynamic properties in the Fe-RE (RE = rare earth metals) binary systems

This study focuses on investigating phase equilibria and thermodynamic stability of intermetallic compounds made of the transition metal Fe and rare earth (RE) elements. By using the CALPHAD method and reliable experimental information from the literature, the binary systems of Fe-Y, Fe-Er, and Fe-Lu were reassessed. To improve our previous calculations of Fe-RE (RE = Tb and Dy) binary systems, the Gibbs energy expressions of intermetallic compounds Fe2Tb and Fe2Dy were modified to avoid artificial breaks in their heat capacity curves. Thermodynamic parameters obtained are self-consistent, and the Gibbs energies of the Fe-RE (RE = Tb, Dy, Er, Lu, and Y) phases were accurately expressed to reappear available both thermodynamic data and phase equilibria. This work was further combined with the previous calculations of the Fe-RE (RE = La, Ce, Pr, Nd, Sm, Gd, Ho, and Tm) systems to discuss thermodynamic characteristics and phase equilibria of Fe-RE binary systems in detail. A trend was noticed for the change of thermodynamic properties and phase equilibria of the Fe-RE binary systems with RE atomic number. Generally, as the RE atomic number increases, the formation temperatures of the Fe-RE intermetallic compounds increase gradually, and the enthalpy of mixing of liquid Fe-RE (apart from Fe-Y and Fe-Ce) alloys and the enthalpy of formation of the Fe-RE (apart from Fe-Y, Fe-Ce, Fe-Gd, and Fe-Dy) intermetallic compounds become increasingly negative. The results provide a thorough set of thermodynamic parameters of thirteen Fe-RE binary systems, which could serve as a sound basis for developing a thermodynamic database of Fe-RE-based alloy systems.

Heat Capacity and Thermodynamic Functions of Titanium-Manganites of Lanthanum, Lithium and Sodium of LaLi2TiMnO6 and LaNa2TiMnO6.

Titanium-manganites of LaLi2TiMnO6 and LaNa2TiMnO6 were synthesized by the methods of ceramic technology from the oxides of lanthanum, titanium (IV), manganese (III), and the carbonates of lithium and sodium. The types of their syngony and the parameters of their gratings were determined radiographically. The isobaric heat capacities of titanium-manganites were measured with experimental calorimetry in the range of 298.15-673 K. It was found that on the dependence curve of heat capacity versus temperature of C°p~f(T), for LaLi2TiMnO6 at 348 K and 598 K, and LaNa2TiMnO6 at 348 K, there are abnormal jumps in heat capacity, probably related to phase transitions of the second kind. Taking into account the temperatures of the phase transitions, the equations of the temperature dependence of the heat capacity of titanium-manganites were derived. Their standard entropies were calculated by the ion increments method. Temperature dependences of the thermodynamic functions of S°(T), H°(T)-H°(298.15), and Φxx(T) were calculated using the experimental data on heat capacities and the calculated values of the standard entropies. The standard heat capacities of the studied compounds were calculated by the independent methods of ion increments and Debye, the values of which were in satisfactory agreement with the experimental data. The standard enthalpy of the formation of LaLi2TiMnO6 and LaNa2TiMnO6 was calculated according to the methodology developed by the authors. The conducted electrophysical studies determined the nature of the second-order phase transition and the semiconductor features of their conductivity. Thus, all the above-mentioned data on the experimental and calculated studies of the temperature dependence of heat capacity, the thermodynamic functions to determine a standard enthalpy of formation of LaLi2TiMnO6 and LaNa2TiMnO6, and the investigation of their electrical properties are absolutely new, and they have no analogues.

Subcooling Effect on PCM Solidification: A Thermostat-like Approach to Thermal Energy Storage

Choosing the right phase change material (PCM) for a thermal energy storage (TES) application is a crucial step in guaranteeing the effectiveness of the system. Among a variety of PCMs available, the choice for a given application is established by several key factors, e.g., latent heat, stability, and melting point. However, phenomena such as subcooling—for which PCM cools in a liquid state below its solidification point—can lead to a reduction in the amount of energy stored or released, reducing the TES overall effectiveness, and also in some inaccuracies when modeling the problem. Thus, understanding the effects of subcooling on PCM performance is crucial for modeling and optimizing the design and the performance of TES systems. To this end, this work analyzes the PCM discharging phase in a cold thermal energy storage coupled to a chiller system. A first conduction-based predictive model is developed based on enthalpy–porosity formulation. Subcooling phenomena are encompassed through a control variable formulation, which takes its cue from the operation of a thermostat. Then, thermal properties of the PCM, i.e., the phase change range and specific heat capacity curve with temperature, are evaluated by using differential scanning calorimetry (DSC), in order to derive a second predictive model based on these new data, without including subcooling, for the sake of comparison with the first one. Experimental results from the storage tank confirm both model reliability and the fact that the PCM suffers from subcooling. Between the two numerical models developed, the first one that considers subcooling proves it is able to predict with satisfactory accuracy (RMSE &lt; 1 °C) the temperature evolution on different tank levels.

Critical behavior of AdS black holes surrounded by dark fluid with Chaplygin-like equation of state

Supposing the existence of Dark Fluid with a Chaplygin-like equation of state $p=-B/\rho$ (CDF) as a cosmic background, we obtain a static spherically-symmetric black hole (BH) solution to the Einstein gravitational equations. We study the $P-V$ critical behavior of AdS BH surrounded by the CDF in the extended phase space where the cosmological constant appears as pressure, and our results show the existence of the Van der Waals like small/large BH phase transition. Also, it is found that such a BH displays a first-order low/high-$\Phi$ BH phase transition and admits the same criticality with van der Waals liquid/gas system in the non-extended phase space, where the normalization factor $q$ is considered as a thermodynamic variable, while the cosmological constant being fixed. In both $P-V$ and the newly proposed $q-\Phi$ phase spaces, we calculate the BH equations of state and then numerically study the corresponding critical quantities. Moreover, the critical exponents are derived and the results show the universal class of the scaling behavior of thermodynamic quantities near criticality. Finally, we study the shadow thermodynamics of AdS BHs surrounded by the CDF. We find that, there exists a positive correlation between the shadow radius and the event horizon radius in our case. By analyzing the temperature and heat capacity curves under the shadow context, we discover that the shadow radius can replace the event horizon radius to demonstrate the BH phase transition process, and the changes of the shadow radius can serve as order parameters for the small/large BH phase transition, indicating that the shadow radius could give us a glimpse into the BH phase structure from the observational point of view.

Formation of trapped meta-stable liquid–vapour interfaces in polar liquids in presence of excess gas-like molecules: Anomalous heat capacities and emergence of microscopic bubbles

We have elucidated the wetting behaviour of a polar-liquid in contact of an attractive planar surface. The formation of meta-stable liquid column-like structures, separated by vapour phase molecules, forming liquid–vapor interfaces, has been investigated in confined planar geometry. We have used lattice based Monte Carlo simulation for both canonical and grand-canonical systems. The presence of excess gas-like molecules has been reported to alter partial wetting conditions due to excess pressure in canonical ensemble. The system is driven towards formation of microscopic liquid–vapor interfaces, and the distinct liquid–vapor interface forming bridge-like structures disappear at high temperatures. The existence of meta-stable interfaces and meso- and nano-scale liquid structures under confinement appears to be a direct manifestation of the restricted movement of the molecules. We conclude that associated irreversibility due to stacking of atoms in extremely narrow geometries results into formation of meta-stable equilibrium structures. The negative heat capacities reduce at lower temperatures. Further it also depends on the extent of vapor phase as well as presence of gas-like molecules. Adsorption isotherm for liquid molecules adsorbed at the first layer of the attractive surface confirms that the negative heat capacities are rooted into the formation of trapped meta-stable states due to complete wetting of the surface due to adsorption of liquid molecules at first (few) layers of the surface. Due to the inaccessibility of the microstates, the system is trapped into a meta-stable or quasi-equilibrium state. The final structure is an outcome of the reconciliation between molecular interactions, interfacial energies and the extent of physical confinement. The micrographs and density profiles recorded at different temperatures T = 1.0, 1.2, 1.4 and 1.6, phase-coexistence, specific heat capacity and configurational entropy curves confirm for the same. The computational model for our case study fully explores the origin of the interfaces and successfully accounts definite reasons for the associated negative heat capacities, which has been riddling scientist for many decades.

Universal behavior of low-temperature heat capacity of acrylonitrile-butadiene-styrene thermoplastic polymer and its composite with graphene oxide

The low-temperature dependence of the heat capacity of acrylonitrile-butadiene-styrene (ABS) polymer and its composite with thermally reduced graphene oxide was studied. The existence of a so-called “boson peak” characteristic of orientational and structural glasses was demonstrated. The boson peak appears in the form of a local maximum in the heat capacity curve displayed as C/T3 vs T at Tmax = 3.52 K. It was found that for both ABS polymer and its composite, as well as for a number of other substances of a crystalline and amorphous nature, the manifestation of the anomaly of the boson peak in the heat capacity has a universal character that is described by an empirical function Δ*. The value of Δ* depends on the magnitude of the anomaly in the heat capacity and the temperature of the boson peak manifestation. Thus, this study provides new physical information about the possible causes of the boson peak appearance in disordered materials and indicates the universality of boson peak anomaly for substances with short- and long-range order.

Magnetic and dielectric properties double perovskite Sr&lt;sub&gt;2&lt;/sub&gt;MnTiO&lt;sub&gt;5.87&lt;/sub&gt;

Magnetic and dielectric properties of Sr2MnTiO5.87 double perovskite have been studied. Magnetic phase transitions were observed at 12 and 43 K in the FC and ZFC curves of magnetization and magnetic heat capacity, the nature of which is being discussed. From the analysis of the lattice contribution to the specific heat, the Debye and Einstein temperatures were determined, which were θD = 217 К, θЕ1 = 275 К, θЕ2 = 615 К, θЕ3 = 2000 К.