Behavior Of Heat Capacity Research Articles

Effect of surface wettability on specific heat capacity of nano-confined liquid

Equilibrium Molecular Dynamics (EMD) simulations are carried out to investigate the effects of wall wettability and nanogap thickness (h) on the constant volume molar heat capacity (Cv) of liquid argon entrapped between two solid copper walls at a fixed temperature of 100 K. Lennard-Jones (LJ) potential is employed to model the interaction between atoms, with nanogap thickness (h) varying between 0.585 nm to 5.85 nm. To characterize interfacial surface wettability as hydrophobic or hydrophilic, the solid-liquid interaction potential has been altered, and its effect on molar heat capacity (Cv) has been evaluated. Simulation results reveal three key findings. As the surface becomes more hydrophobic (i) both maximum heat capacity (Cv,max), and critical nanogap thickness (hc) (nanogap thickness at which maximum heat capacity is obtained) decrease; (ii) the range of nanogap thickness where the heat capacity of nanoconfined liquid surpasses that of bulk liquid diminishes; (iii) the heat capacity of nanoconfined liquid tends to match its bulk equivalent. This anomalous behavior of heat capacity with changing wall wettability is explained by variation in both vibrational (mode of phonon transportation) and configurational (density oscillation near the wall, thermal boundary resistance, molecular mobility, etc.) contribution of nanoconfined liquid.

Towards a Better Understanding of Texturization during High-Moisture Extrusion (HME)-Part I: Modeling the Texturability of Plant-Based Proteins.

This study focused on predicting high-moisture texturization of plant-based proteins (soy protein concentrate (SPC), soy protein isolate (SPI), pea protein isolate (PPI)) at different water contents (57.5%, 60%, 65%, 70%, and 72.5% (w/w db)) to optimize and guarantee the production of high-moisture meat analogs (HMMA). Therefore, high-moisture extrusion (HME) experiments were performed, and the texture of the obtained high-moisture extruded samples (HMES) was sensory evaluated and categorized into poorly-textured, textured, or well-textured. In parallel, data on heat capacity (cp) and phase transition behavior of the plant-based proteins were determined using differential scanning calorimetry (DSC). Based on the DSC data, a model for predicting cp of hydrated, but not extruded, plant-based proteins was developed. Furthermore, based on the aforementioned model for predicting cp and DSC data on phase transition behavior of the plant-based proteins in combination with conducted HME trials and the mentioned model for predicting cp, a texturization indicator was developed, which could be used to calculate the minimum threshold temperature required to texturize plant-based proteins during HME. The outcome of this study could help to minimize the resources of expensive extrusion trials in the industry to produce HMMA with defined textures.

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.

A priori and a posteriori analysis of flamelet modeling for large-eddy simulations of a non-adiabatic backward-facing step

A lean premixed ethylene–air flame in a backstep configuration is simulated on multiple grids using both direct numerical simulations (DNS) with reduced order kinetic mechanism and large eddy simulations (LES) with flamelet-based thermochemistry. The configuration includes preheated reactants and a recirculation zone that provides radicals and high temperature gases to stabilize the flame. Heat losses are present due to the proximity of cooled walls. The reacting flow obtained from DNS at different resolutions is first analyzed to investigate the property of heat transfer within the recirculation region. LES based on adiabatic flamelets with a correction of the heat capacity is then tested, and its ability to account for heat losses is compared to results obtained using a three-dimensional non-adiabatic flamelet approach. Mean fields and subgrid properties are compared to those obtained from DNS to assess the capability of the LES models. The results show that the non-adiabatic flamelet approach can predict recirculation region and temperature fields with good accuracy. The model with heat capacity correction is able to effectively correct the heat capacity behavior as observed by a priori comparisons. However, in the a posteriori context, it is observed to overestimate the temperature field, although the correct size of the recirculation region is predicted. The combined a priori and a posteriori analyses on the same configuration and at different mesh resolutions allow for a precise separation of modeling effects due to heat transfer at the wall and combustion closure, thus providing indications on the LES performance in the context of flamelets.

Features of Ca1-xYxF2+x solid solution heat capacity behavior: diffuse phase transition

Features of Ca1-xYxF2+x solid solution heat capacity behavior: diffuse phase transition

Magnetic frustration driven by conduction carrier blocking in Nd2Co0.85Si2.88

The intermetallic compound ${\mathrm{Nd}}_{2}{\mathrm{Co}}_{0.85}{\mathrm{Si}}_{2.88}$ having a triangular lattice could be synthesized in single phase only with defect crystal structure. Investigation through different experimental techniques indicate the presence of two magnetic transitions in the system. As verified experimentally and theoretically, the high-temperature transition ${T}_{\mathrm{H}}\ensuremath{\sim}$ 140 K is associated with the development of ferromagnetic interaction between itinerant Co moments, whereas the low-temperature transition at ${T}_{\mathrm{L}}\ensuremath{\sim}$ 6.5 K is due to the coupling among $\text{Nd}\text{\ensuremath{-}}4f$ and $\mathrm{Co}\text{\ensuremath{-}}3d$ moments, which is antiferromagnetic in nature. Detailed studies of temperature-dependent dc magnetic susceptibility, field dependence of isothermal magnetization, nonequilibrium dynamical behavior, viz., magnetic relaxation, aging effect, magnetic-memory effect, and temperature dependence of heat capacity, along with density functional theory (DFT) calculations, suggest that the ground state is magnetically frustrated spin glass in nature, having competing magnetic interactions of equivalent energies. DFT results further reveal that the $3d/5d$-conduction carriers are blocked in the system and act as a barrier for the $4f\text{\ensuremath{-}}4f$ RKKY interactions, resulting in spin frustration. Presence of vacancy defects in the crystal are also conducive to the spin frustration. This is an unique mechanism of magnetic frustration, not emphasized so far in any of the ternary ${R}_{2}T{X}_{3}$ ($R$ = rare earth, $T$ = transition elements, and $X$ = Si, Ge, In) type compounds. Due to the competing character of the itinerant $3d$ and localized $4f$ moments, the compound exhibits anomalous field dependence of magnetic coercivity. The system also exhibits a considerable magnetic entropy change of $\ensuremath{-}\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{M}}\ensuremath{\sim}$ 13.3 J/kg K with a relative cooling power (RCP) of 220 J/kg and adiabatic temperature change $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{ad}}$ of 6 K for magnetic field change of 70 kOe.

Quantum Griffiths phase in disordered Mn1−xFexSi

We show the presence of magnetic rare regions consistent with the quantum Griffiths phase in Fe-doped MnSi using detailed heat capacity, magnetization, and muon spin relaxation (\ensuremath{\mu}SR) measurements down to millikelvin temperatures. The slow dynamics of these rare regions at low temperatures leads to the non-Fermi-liquid behavior in heat capacity and magnetization. The \ensuremath{\mu}SR and magnetization results further indicate that the dynamics freezes into a cluster-glass state below ${T}_{f}\ensuremath{\sim}1.25$ K. The results are in agreement with theoretical models proposed in the literature for metallic systems with Heisenberg symmetry that exhibit the quantum Griffiths phase in the presence of strong disorder.

Distinct magnetic relaxation behaviors in nitronyl nitroxide-based cocrystalline supramolecular system with DyIII-O-H⋯O-N hydrogen bond

The self-assembly of Dy(hfac)3·2H2O, Co(hfac)2·2H2O or Mn(hfac)2·2H2O (hfac = hexafiuoroacetylacetonate) with NITPh-triazole radical (NITPh-triazole = 2-[2-(1H-1,2,4-triazol-1-yl)phenyl]-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) produces two 2p-3d-4f compounds of formula {[Dy(hfac)3(H2O)2][Co2(hfac)4(NITPh-triazole)2]2.CH2Cl2}n (1) and {[Dy(hfac)3(H2O)2][Mn2(hfac)4(NITPh-triazole)2]2}n (2) featuring extraordinary intermolecular hydrogen bonds between coordinated H2O molecules and uncoordinated NO groups linking into a supramolecular one-dimensional chain. Notably, the LnIII-O-H⋯O-N hydrogen bond bridge has been rarely observed in nitronyl nitroxide-metal system. Magnetic performance and heat capacity of both 2p-3d-4f compounds are detected. Interestingly, 1 and 2 both show apparent double peaks of χ′′ signals with two-step magnetic relaxation processes. Furthermore, the effective barrier of 1 is obviously higher than 2. As far as we know, employing unusual intermolecular LnIII-O-H⋯O-N hydrogen bond, it is the first to obtain supramolecular 2p-3d-4f one-dimensional heterospin materials with apparent slow magnetic relaxation and heat capacity behaviors.

Heat Capacities of L-Cysteine, L-Serine, L-Threonine, L-Lysine, and L-Methionine.

In an effort to establish reliable thermodynamic data for amino acids, heat capacity and phase behavior are reported for L-cysteine (CAS RN: 52-90-4), L-serine (CAS RN: 56-45-1), L-threonine (CAS RN: 72-19-5), L-lysine (CAS RN: 56-87-1), and L-methionine (CAS RN: 63-68-3). Prior to heat capacity measurements, initial crystal structures were identified by X-ray powder diffraction, followed by a thorough investigation of the polymorphic behavior using differential scanning calorimetry in the temperature range from 183 K to the decomposition temperature determined by thermogravimetric analysis. Crystal heat capacities of all five amino acids were measured by Tian-Calvet calorimetry in the temperature interval (262-358) K and by power compensation DSC in the temperature interval from 215 K to over 420 K. Experimental values of this work were compared and combined with the literature data obtained with adiabatic calorimetry. Low-temperature heat capacities of L-threonine and L-lysine, for which no or limited literature data was available, were measured using the relaxation (heat pulse) calorimetry. As a result, reference heat capacities and thermodynamic functions for the crystalline phase from near 0 K to over 420 K were developed.

On the classical critical behavior of the specific heat capacity of a model of structural phase transitions with a long-range interaction

The critical specific heat capacity c of a d-dimensional model describing structural phase transitions in an anharmonic crystal with a long-range interaction (decreasing at large distances r as r −d−σ , 0 < σ ≤ 2) is studied near the classical critical point Tc . At temperatures T > Tc and for dimensions σ < d < 2σ (σ and 2σ are the lower and the upper critical dimensions, respectively) the critical specific heat capacity is obtained in the form c ≈ 1 − Dεαs , where D > 0 and αs < 0 depend only on the ratio d/σ, and ε = T/Tc −1 is a measure of the deviation from the critical point. For three fixed values of the ratio d/σ the dependence c ≈ c(ε) is graphically presented. It is shown that at all temperatures T ≤ Tc the specific heat capacity retains its maximum value, c max = 1. The critical exponent αs , obtained here, coincides with that of the known mean spherical model, while c max is different for the two models.

Measurements of Isothermal Vapor–Liquid Equilibrium and Critical Point-Based Perturbed-Chain Statistical Association Fluid Theory Phase Behavior Modeling of the Propane + Phenol and Tetracosane + Propane/n-Butane Mixtures

The isothermal vapor–liquid equilibrium (VLE, pressure, temperature, and composition of coexisting vapor and liquid phases, PTxy) was directly determined using a high-pressure optical cell for binary propane + phenol and ternary tetracosane + propane/n-butane systems. Measurements were carried out at three selected isotherms of 383.15, 403.15, and 423.15 K at pressures from 0.94 to 14.5 MPa for propane + phenol and 403.15, 423.15, and 443.15 K at pressures up to 7.5 MPa for tetracosane + propane/n-butane systems. The critical property data (TC and PC) for both mixtures have been derived from the measured VLE data. Based on the initial slopes of the critical lines (shape of the critical lines), the qualitative behavior (pure- and mixture-like behavior) of the isochoric heat capacity (CVx, weak singular property), isobaric heat capacity (CPx), and isothermal compressibility (KTx, strong singular property) of the propane + phenol binary mixture near the critical point has been studied. It is demonstrated that the simplest version of critical point-based perturbed-chain statistical association fluid theory neglecting the complex molecular background of phenol yields reasonably accurate predictions of its pure compound properties. With the value of k12 obtained by fitting the present data of propane + phenol, this model yields reliable predictions for VLE in the systems of other n-alkanes, benzene, carbon monoxide, and nitrogen.

Black holes in 4D AdS Einstein Gauss Bonnet gravity with power: Yang Mills field

In this paper we construct an exact spherically symmetric black hole solution with a power Yang–Mills (YM) source in the context of 4D Einstein Gauss–Bonnet gravity (4D EGB). We choose our source as \((F_{\mu \nu }^{(a)}F^{\mu \nu (a)})^q\), where q is an arbitrary positive real number. Thereafter we study the horizon structure, thermodynamic issues like thermal stability and black hole phase transition. Our purpose here is to analyse the black hole space-time under the net effect coming from the Gauss–Bonnet coupling parameter \(\alpha \) and the nonlinear parameter q. We then evaluate all important thermodynamic quantities to establish the Smarr formula and the first law of thermodynamics in extended phase space. The behaviour of heat capacity as a function of horizon radius is thoroughly studied to understand the thermal stability of the black hole solution. An interesting phenomena of existence/absence of thermal phase transition occur due to the nonlinearity of YM source. For some values of the parameters, we find that the solution exhibits a first-order phase transition, like a van der Waals fluid. In addition, we also verify Maxwell’s equal area law numerically by crucial analysis of Gibbs free energy as a function of temperature. Moreover, the critical exponents are derived and showed the universality class of the scaling behaviour of thermodynamic quantities near criticality.

Study of thermodynamical geometries of conformal gravity black hole

This work deals with the applications of thermodynamical geometries on conformal gravity black holes (CGBH) consisting of conformal parameters a and k. The stability of black hole (BH) addressed with the aid of small, middle, large and divergency roots, respectively. For this purpose, graphical behavior of heat capacity and temperature versus horizon radius is presented which help us to show the stability conditions. Further, studied the different geometries like Weinhold, Ruppeiner, Geometrothermodynamics (GTD) and Hendi-Panahiyah-Eslam-Momennia (HPEM), and found relationship between divergency of scalar curvature and zeros of heat capacity. As a result, it is noticed that Ruppeiner, HPEM and GTD metric exhibit more important information as compared to Weinhold.

Vacancy-Driven Disorder and Elevated Dielectric Response in the Pyrochlore Pb1.5Nb2O6.5.

Lone pair-driven distortions are a hallmark of many technologically important lead (Pb)-based materials. The role of Pb2+ in polar perovskites is well understood and easily manipulated for applications in piezo- and ferroelectricity, but the control of ordered lone pair behavior in Pb-based pyrochlores is less clear. Crystallographically and geometrically more complex than the perovskite structure, the pyrochlore structure is prone to geometric frustration of local dipoles due to a triangular arrangement of cations on a diamond lattice. The role of vacancies on the O' site of the pyrochlore network has been implicated as an important driver for the expression and correlation of stereochemically active lone pairs in pyrochlores such as Pb2Ru2O6.5 and Pb2Sn2O6. In this work we report on the structural, dielectric, and heat capacity behavior of the cation- and anion-deficient pyrochlore Pb1.5Nb2O6.5 upon cooling. We find that local distortions are present at all temperatures that can be described by cristobalite-type cation ordering, and this ordering persists to longer length scales upon cooling. From a crystallographic perspective, the material remains disordered and does not undergo an observable phase transition. In combination with density function calculations, we propose that the stereochemical activity of the Pb2+ lone pairs is driven by proximity to O' vacancies, and the crystallographic site disorder of the O' vacancies prohibits long range correlation of lone pair-driven distortions. This in turn prevents a low-temperature phase transition and results in an elevated dielectric permittivity across a broad temperature range.

Glass transition as a topological phase transition.

The glass transition is described as a phase transition in the system of topologically protected excitations in matter structure. The critical behavior of the system is considered in both static and dynamic cases. It is shown that the proposed model reproduces most of the characteristic thermodynamic and kinetic properties of glass transition: the Vogel-Fulcher-Tammann law, the behavior of susceptibility and nonlinear susceptibilities, and heat capacity behavior as well as the appearance of a boson peak in the frequency dependence of the dynamic structure factor near the glass transition temperature.

Magneto-transport and Thermal properties of TiH diatomic molecule under the influence of magnetic and Aharonov-Bohm (AB) fields

In this study, the effects of Aharonov-Bohm (AB) and magnetic fields on the thermodynamic and magneto-transport properties of TiH diatomic molecule using the Deng-Fan potential as a model are investigated. The functional analysis approach (FAA) is used to solve the Schrodinger equation in the presence of magnetic and AB fields with Deng-Fan potential. The energy equation, as well as the wave function, have been derived. The analytic expressions for the thermo-magnetic and transport properties of the Deng-Fan potential are derived using the energy equation and the partition function. These properties obtained are thoroughly analysed utilising graphical representations. Our analysis shows that the magnetic susceptibility of the TiH exhibits a diamagnetic behaviour, and the specific heat capacity behaviour agrees with the famous Dulong-Petit law when the system is subjected to AB field variations and a fixed magnetic field. Albeit, a slight anomaly is observed in the behaviour of the specific heat capacity. Our findings will be valuable in various fields of physics, including chemical and molecular physics and condensed matter physics, where the derived models could be applied to study other diatomic molecules and quantum dots, respectively.

Thermodynamics and phase transition of d-dimensional charged AdS black hole in rainbow gravity

In this paper, we have studied the thermodynamic properties of charged AdS black hole with different dimensions under rainbow gravity. At first, by employing the Heisenberg uncertainty principle and the modified dispersion relation and analyzing the effect of rainbow gravity parameter [Formula: see text] and AdS radius [Formula: see text] on the thermodynamics and phase transformation, we have found that the phase structure is related to the AdS radius [Formula: see text] and the heat capacity behaviors are quite similar for different rainbow gravity parameters [Formula: see text] and different dimensions [Formula: see text]. Then, for the rainbow gravity, introducing the analogy between the charged AdS black hole and liquid–gas systems and analyzing the critical behavior of the state equation for charged AdS black hole in different dimensions, the charged AdS black hole has Van der Waals-like phase transitions. At last, we have discussed the relationship between Gibbs free energy [Formula: see text] and Hawking temperature [Formula: see text] in different dimensions and found the typical dovetail behavior, which can be interpreted as a first-order phase transition for the charged AdS black hole under rainbow gravity.

Non-Relativistic Treatment of the 2D Electron System Interacting via Varshni–Shukla Potential Using the Asymptotic Iteration Method

The nonrelativistic treatment of the Varshni–Shukla potential (V–SP) in the presence of magnetic and Aharanov–Bohm fields is carried out using the asymptotic iteration method (AIM). The energy equation and wave function are derived analytically. The energy levels are summed to obtain the partition function, which is employed to derive the expressions for the thermomagnetic properties of the V–SP. These properties are analyzed extensively using graphical representations. It is observed that in the various settings of the analysis, the system shows a diamagnetic characteristic, and the specific heat capacity behavior agrees with the recognized Dulong–Petit law, although some slight anomaly is observed. This irregular behavior could be attributed to a Schottky anomaly. Our findings will be valuable in a variety of fields of physics, including chemical, molecular and condensed matter physics, where our derived models could be applied to study other diatomic molecules and quantum dots, respectively.

Influence of the Synthesis and Crystallization Processes on the Cation Distribution in a Series of Multivariate Rare-Earth Metal-Organic Frameworks and Their Magnetic Characterization.

The incorporation of multiple metal atoms in multivariate metal–organic frameworks is typically carried out through a one-pot synthesis procedure that involves the simultaneous reaction of the selected elements with the organic linkers. In order to attain control over the distribution of the elements and to be able to produce materials with controllable metal combinations, it is required to understand the synthetic and crystallization processes. In this work, we have completed a study with the RPF-4 MOF family, which is made of various rare-earth elements, to investigate and determine how the different initial combinations of metal cations result in different atomic distributions in the obtained materials. Thus, we have found that for equimolar combinations involving lanthanum and another rare-earth element, such as ytterbium, gadolinium, or dysprosium, a compositional segregation takes place in the products, resulting in crystals with different compositions. On the contrary, binary combinations of ytterbium, gadolinium, erbium, and dysprosium result in homogeneous distributions. This dissimilar behavior is ascribed to differences in the crystallization pathways through which the MOF is formed. Along with the synthetic and crystallization study and considering the structural features of this MOF family, we also disclose here a comprehensive characterization of the magnetic properties of the compounds and the heat capacity behavior under different external magnetic fields.

Wasp-waisted hysteresis in magnetic materials with octahedral structure: A theoretical explanation based on exactly solvable model

The possibility of the existence of two different but thermodynamically equivalent ferromagnetic-like phases below the critical temperature in magnetic materials with octahedral structure is shown in the framework of an exactly solvable model with the competition between nearest-neighbor ferromagnetic and antiferromagnetic interactions on the octahedral recursive lattice. This observation offers a natural base for a fundamental theoretical explanation of the existence of anomalous wasp-waisted-like hysteresis measured in various perovskites with basic octahedral structure. Besides, it is shown that the corresponding ground states are highly macroscopically degenerated. This leads to the presence of frustration effects in the model thermodynamics in their vicinity. In this respect, the anomalous behavior of the specific heat capacity is demonstrated.