Calculation Of Thermodynamic Properties Research Articles

AFLOW-QHA3P: Robust and automated method to compute thermodynamic properties of solids

Accelerating the calculations of finite-temperature thermodynamic properties is a major challenge for rational materials design. Reliable methods can be quite expensive, limiting their effective applicability in autonomous high-throughput workflows. Here, the 3-phonons quasi-harmonic approximation (QHA) method is introduced, requiring only three phonon calculations to obtain a thorough characterization of the material. Leveraging a Taylor expansion of the phonon frequencies around the equilibrium volume, the method efficiently resolves the volumetric thermal expansion coefficient, specific heat at constant pressure, the enthalpy, and bulk modulus. Results from the standard QHA and experiments corroborate the procedure, and additional comparisons are made with the recently developed self-consistent QHA. The three approaches - 3-phonons, standard, and self- consistent QHAs - are all included within the automated, open-source framework AFLOW, allowing automated determination of properties with various implementations within the same framework.

First-principle calculations of structural, electronic, optical and thermodynamical properties of fluorinated graphene

The structural, electronic, optical and thermodynamical properties of three stable structures: chair (C-), boat (B-) and tricycle (T-) of fluorinated graphene (fluorographene) have been studied using first-principle density functional theory (DFT) calculations. The band structure and density of states (DOS) have been discussed. The values of 17 parameters have been studied for all three structures. The thermodynamical properties have been described in temperature range 5 K–1000 K. The optical properties such as dielectric constants, refractive index, birefringence, plasmon energy and absorption edge, and values of all parameters of T-structure have been calculated for the first time. The calculated values are compared with the available experimental and reported values. Reasonably good agreement has been obtained between them.

First-principles calculation of ideal-gas thermodynamic properties of long-chain molecules by R1SM approach-Application to n-alkanes.

First-principles calculations, coupled with statistical thermodynamics, can provide ideal-gas thermodynamic properties but get complicated and less reliable with an increasing number of conformers. An approach designed for calculation of ideal-gas thermodynamic properties of long-chain molecules, R1SM, and its simplified version, sR1SM, is tested in this work by calculation of ideal-gas heat capacities and entropies for a homologous series of n-alkanes up to n-tetradecane. The R1SM approach incorporates the rigid rotor-harmonic oscillator approximation in combination with a correction for internal rotations of methyl tops using the one-dimensional hindered rotor scheme and the mixing model accounting for the population of conformers based on the Boltzmann distribution. The R1SM approach is applicable for compounds with up to hundreds of conformers, while the simplified sR1SM approach can be used for molecules with up to 105 conformers when coupled with rules for enumeration of stable conformers and estimation scheme for their energies. The obtained results for n-alkanes are compared with experimental values and previously employed computational schemes. As the conformational behavior and conformer energies are inherent parts of the proposed approaches, a thorough conformational study of n-alkanes is performed and compared with experiments and the Tasi rules for enumeration of n-alkane conformers. Finally, the standard uncertainty of the R1SM-calculated ideal-gas thermodynamic properties is estimated based on the error propagation from the used input quantities and approximations as well as on comparison to experimental values and amounts to less than 1% for both ideal-gas heat capacity and standard ideal-gas entropy.

Recent Developments in Integral Equation Theory for Solvation to Treat Density Inhomogeneity at Solute–Solvent Interface

AbstractThe integration equation theory (IET) provides highly efficient tools for the calculation of structural and thermodynamic properties of molecular liquids. In recent years, the 3D reference interaction site model (3DRISM), the most developed IET for solvation, has been widely applied to study protein solvation, aggregation, and drug‐receptor binding. However, hydrophobic solutes with sufficient size (>nm) can induce water density depletion at the solute–solvent interface. This density depletion is not considered in the original 3DRISM theory. The authors here review the recent developments of 3DRISM at hydrophobic surfaces and related theories to address this challenge. At hydrophobic surfaces, an additional hydrophobicity‐induced density inhomogeneity equation is introduced to 3DRISM theory to consider this density depletion. Accordingly, several new closures equations including D2 closure and D2MSA closures are developed to enable stable numerical solutions of 3DRISM equations. These newly developed theories hold great promise for an accurate and rapid calculation of the solvation effect for complex molecular systems such as proteins. At the end of the report, the authors also provide a perspective on other challenges of the IETs as an efficient solvation model.

First-principles calculations of elastic and thermodynamic properties under hydrostatic pressure of cubic InNxP1-x ternary alloys

We present a first-principles study of the elastic and thermodynamic properties of the zinc-blend (ZB) InNxP1-x ternary alloy in the full range of 0 ≤ x ≤ 1. Calculations were carried out using WIEN2k code based on a non-relativistic full potential linearized augmented plan wave (FP-LAPW) method within the density functional theory (DFT). The approximation of exchange-correlation energy was performed with Generalized Gradient Approximation (GGA). The elastic constants and related mechanical properties were investigated. We have found that the stiffness coefficients increase with the increase of nitrogen content. The values of the bulk modulus derived from elastic stiffness coefficients are found to be very close to the values derived directly from Murnaghan equation of state, indicating the good accuracy of the Cij coefficients. The elastic properties were also calculated under hydrostatic pressure for (P = 0.00, 5.00, 10.0, 15.0, 20.0, 25.0 GPa). Furthermore, we have performed a quasi-harmonic Debye model calculation using GIBBS2 package to predict the thermodynamic properties and their dependences on the temperature and pressure. Thermodynamic parameters such as the Gibbs free energy, entropy, heat capacity and Debye temperature have been investigated. Our results show a good agreement with available theoretical and experimental data.

Equation of state and thermodynamic properties for mixtures of [formula omitted], [formula omitted], [formula omitted], and [formula omitted] from ambient up to 1000 K and 280 MPa

Supercritical water oxidation (SCWO) is an effective technique to treat wet organic wastes. Its modeling requires an accurate calculation of thermodynamic properties. In this work an equation of state (EOS) is proposed which accurately predicts the thermodynamic state of mixtures of water, oxygen, nitrogen, and carbon dioxide for a wide range of compositions, temperatures, and pressures including supercritical conditions. The EOS includes a volume translation, an evolved α-function and non-quadratic mixing rules. The introduced parameters are regressed to experimental data. From the pressure-explicit EOS, enthalpy, specific heats at constant volume and constant pressure, and fugacity coefficients are derived and calculated. The binary mixtures H2O/O2, H2O/N2, H2O/CO2, N2/CO2 as well as the ternary mixture H2O/O2/N2 are well predicted by the proposed EOS with relative errors below 10% and 15%, respectively. The region of low temperature and high pressure is most difficult to predict with relative errors up to 20%.

First-principles calculations of structural, elastic and thermodynamic properties of (h, r)-TiAl2

In this work, based on density functional theory (DFT) within generalized gradient approximation (GGA), the first-principles calculations were employed to calculate the structural properties, phase stabilities, electronic, elastic and thermodynamic properties of (h, r)-TiAl2. According to calculated formation enthalpies, r-TiAl2 possesses higher stability. What's more, the values of Cauchy pressures, Poisson's ratio ν and the B/G ratio illustrate that (h, r)-TiAl2 are brittle. The single-crystal and polycrystalline elastic moduli indicate that they take possession of same mechanical properties. Besides, the variations of volume, bulk modulus, heat capacity at constant pressure or volume and Debye temperature as a function of temperature ranging from 0 to 1500 K and pressure ranging from 0 to 50 GPa was also investigated by employing Quasi-harmonic Debye model.

DFT calculations of structural, optoelectronic and thermodynamic properties of BxAl1-xP alloys

The structural, optoelectronic and thermodynamic properties of the ternary alloys BxAl1-xP are investigated using the Full-potential linear muffin-tin orbital (FP-LMTO) method within density functional theory (DFT) in the zinc-blende structure. The exchange and correlation potentials are treated by the local density approximation (LDA) and generalized gradient approximations (GGA). The ground state properties of BxAl1-xP are determined and compared with the available data. The electronic structure have been investigated and discussed in details. The optical constants, including the dielectric function ε(w) and the refractive index n(w) are calculated and we found that our compounds are potential usefulness in optoelectronic applications. Furthermore, we have analyzed the thermodynamic properties by the quasi-harmonic Debye model.

Ab initio calculations of hardness, elastic, thermodynamic and electronic properties of metal nitrides (XN2; X = Pd, Pt) under high-pressure

We have performed first-principles calculations within density functional theory (DFT) to investigate the hardness, elastic, thermodynamic and electronic properties of metal nitrides compounds (XN2; X = Pd, Pt) in pyrite structure, under high hydrostatic pressure. The calculated structural properties match with those previously reported experimental and theoretical data. The Vickers hardness of PdN2 and PtN2 compounds were calculated in 7.5 and 27.7 GPa, respectively. We also calculated the electronic properties of both compounds. The calculated electronic band structure of PtN2 at either 0 GPa or 153 GPa reveals that this compound is an indirect semiconductor. The top of the valence band is located at M point, whereas the bottom of the conduction band at Λ point at zero pressure or at Σ point at 153 GPa. In the case of PdN2, it was found a conductor-semiconductor transition at 104 GPa.

First-principles calculations of mechanical and thermodynamic properties of tetragonal Be12Ti

The elastic and thermodynamic properties of tetragonal Be12Ti under high temperature and pressure are investigated by first-principles calculations based on pseudopotential plane-wave density functional theory (DFT) within the generalized gradient approximation (GGA) and quasi-harmonic approximation (QHA). The calculated lattice parameters and bulk modulus are in good agreement with the available experimental data. The calculated elastic constants of Be12Ti increase monotonously with increasing pressure, and the elastic stability criterion and the phonon dispersion calculation show that the Be12Ti crystal satisfies the mechanical and dynamic stability under applied pressure (0–100 GPa). The related mechanical properties such as bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) are also studied for polycrystalline of Be12Ti; the calculated B/G value shows that Be12Ti behaves in a brittle manner, and higher pressure can significantly improve the brittleness of Be12Ti. The elastic anisotropy is demonstrated by the elastic anisotropy factors. The direction-dependent Young's modulus and bulk modulus of Be12Ti are dealt with in detail under pressure from 0 GPa to 100 GPa. The pressure and temperature dependencies of the relative volume, the bulk modulus, the elastic constants, the heat capacity and the thermal expansion coefficient, as well as the entropy are obtained and discussed using the quasi-harmonic approximation in the ranges of temperature 0–1600 K and pressure 0–100 GPa.

Optical and nonlinear optical properties of Ln(Tp)2, where Ln = La,…,Lu and Tp = tris(pyrazolyl)borate: a DFT+TD-DFT study

DFT calculations of electronic, structural, thermodynamic properties, magnetic moment, static and dynamic polarizability and hyperpolarizability of Ln(Tp)2 (Ln = rare earths, Tp = ring-unsubstituted tris(pyrazolyl)borate) complexes.

Thermodynamic properties calculation of perrhenates and their application in the simulation of sample pretreatment for the chemical analysis

Thermodynamic properties, namely standard molar enthalpy of formation (Δ H f ° 298 ), standard molar entropy ( S ° 298 ), and temperature dependence of heat capacity ( С р ( Т )) of crystalline metal perrhenates, were assessed by the semi-empirical methods. In this work, Δ H f ° 298 , S ° 298 and coefficients a , b and c for C p = а + 0.001× b × T + 10 5 × c × T – 2 equation were calculated using several methods and averaged. These thermodynamic properties were calculated for the following perrhenates metals: Li, N, K, Rb, Cs, Cu, Ba, Fe, Ca, Cd, Co, Mg, Mn, Pb, Sr, Zn, Al, Crи Fe. The calculated values of the thermodynamic properties were in good accordance with the known literature data. New data were applied to the thermodynamic simulation of rhenium-containing sample pretreatment processes for the chemical analysis. The thermodynamic simulation of the sintering sample with the magnesium oxide with/without oxidizing agents was carried out using HSC 6.1 software with new data about the perrhenates. According to the calculated results, the addition of the oxidizing agent (NaNO 3 or K 2 S 2 O 7 ) to the magnesium oxide was needed and its presence ensured the rhenium transition into the solution without losses. In this case, rhenium was present at the temperature of the sintering predominantly as NaReO 4 c or KReO 4 c . Calculation results and estimation of perrhenates thermodynamic properties could be used for the thermodynamic simulation of different processes as well as in analytical chemistry and in metallurgy. Keywords : perrhenates, thermodynamic properties, thermodynamic simulation, sintering, oxidizing agent, rhenium (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.015 O.V. Melchakova 1 , P.V. Zaitceva 1 , A.V. Maiorova 1,2 , T.V. Kulikova 1,2 , N.V. Pechishcheva 1 , K.Yu. Shunyaev 1,2 1 Institute of Metallurgy of the Ural Branch of the Russian academy of Sciences, 101, Amundsen street, Ekaterinburg, 620016, Russian Federation, 2 Ural Federal University named after the first President of Russia B.N. Yeltsin, 19, Mira street, Ekaterinburg, 620002, Russian Federation

Modeling hydrocarbon droplet dissolution in near-critical or supercritical water using GCA-EOS and non-ideal diffusional driving force in binary mixtures

In this work, the mixing of a hydrocarbon droplet in near- and super-critical water (NCW/SCW) is mathematically modeled, coupling thermodynamic properties calculation with transport processes. In non-ideal systems, mass transfer is captured using the generalized Maxwell-Stefan equations with the driving force expressed in terms of the fugacity gradients. The GCA-EOS is used to predict the thermodynamic properties and phase equilibrium compositions. We select n-decane, n-triacontane, benzene, naphthalene and 1-decylnaphthalene as representative hydrocarbons. Our simulations show delayed mixing processes as the temperature approaches the upper critical solution temperature (UCST) of the mixture, consistent with the impact of non-ideal diffusional driving forces evaluated from pure thermodynamic calculations. Results also show that the phase behavior notably affects the non-ideal driving forces near the UCST, which confirms the importance of coupling accurate thermodynamic models in predictive mixing studies.

The interaction between chitosan and tannic acid calculated based on the density functional theory

This paper presented a study of the interaction between tannic acid and chitosan in flocculation process at molecular level. Gallic acid (GA) was selected as tannic monomer and dimer chitosan was selected as the chitosan for simulation based on the density functional theory. Molecular electrostatic potential analysis was conducted to clarify the active interaction site and the possible atoms formed hydrogen bond. A series of analysis were performed to reveal the non-covalent interaction between GA and chitosan, including calculation of statistic thermodynamic properties under solvent effect, reduced density gradient (RDG) analysis, independent gradient model (IGM) analysis and symmetry adapted perturbation theory (SAPT) energy decomposition analysis. It was concluded that electrostatic interactions was the main driving energy in the tannic acid flocculation process, its contribution is about 55.5% in total attractive energies. Besides, the dispersion and induction interaction were also crucial for the complex stabilization.

A Nonextensive Electrolyte UNIQUAC Model for Prediction of Mean Activity Coefficients of Binary Electrolyte Solutions

In this work, an electrolyte-UNIQUAC model was developed by replacement of Boltzmann weight binary interaction parameters by the nonextensive Tsallis weight. A summation of the long-range electrostatic term (Debye-Huckel equation) and a short-range interaction term were considered in the calculation of thermodynamic properties. A framework proposed by Chen and co-workers was employed for the derivation of the local mole fractions. Application of the nonextensive theory increased the degree of freedom of the present model (T-E-UNIQUAC). Furthermore, the strength of the model lies in its ability to calculate individual activity coefficients of ions. The applicability of the T-E-UNIQUAC model has been tested using aqueous electrolyte solutions and results have been compared with Messnaoui, Chen and Pitzer models.

Qha: A Python package for quasiharmonic free energy calculation for multi-configuration systems

In this work, we present a Python package, qha, which can calculate the equation of state and various thermodynamic properties of both single- and multi-configuration crystalline materials within a user-specified pressure and temperature range in the framework of the quasi-harmonic approximation (QHA). Two examples, one for single-configuration calculation and the other for multi-configuration calculation, are also distributed along with source code. Apart from its versatility, qha has been tested to be both accurate and computationally efficient. Program summaryProgram Title:qhaProgram Files doi:http://dx.doi.org/10.17632/rz42b97px5.1Licensing provisions: GPLv3Programming language: Python3Nature of problem: Calculations of thermodynamic properties of dynamically stable and structurally disordered solids, e.g., H-disordered phases of H2O-ice, solid solutions, defects with multiple possible configurations need to sample the phase space of all relevant configurations. These calculations start from a calculation of the partition function, which includes all structural and vibrational states and from which the Helmholtz free energy and all thermodynamics properties are derived within the quasi-harmonic approximations for a user-defined temperature and pressure range.Solution method: The method involves the calculation of the partition function of a harmonic oscillator along with the calculated energy and vibrational spectra of multiple crystalline configurations to derive the Helmholtz free energy F(Vi,Tj), where i labels the discrete set of volumes and j labels ionic temperature. The free energy is then fit to temperature-dependent finite-strain equations of state from which all thermodynamic properties can be derived.Additional comments including restrictions and unusual features: The package contains executable scripts that can be run directly in the command line given input data and a computational settings file. It can also be separated into stand-alone modules for incorporating into other programs. Though the package is written in Python, it does not seem to be slow since the just-in-time (JIT) compilation technique is used to improve its performance significantly.

Novel solid–solid phase-change cascade systems for high-temperature thermal energy storage

In this work, we investigate novel solid–solid phase-change cascade systems based on mixtures of lithium and sodium sulfates. Solid–solid phase-change materials (PCMs) can be coupled with concentrated solar power technologies. They present several advantages over solid–liquid PCMs including lower thermal expansion, lower or no corrosiveness, and no need for encapsulation. In solid–solid PCMs, the energy is stored during crystal structure transitions. Specifically, lithium sulfate undergoes a crystal structure transition (monoclinic to cubic) at 576 °C, which is a suitable temperature for concentrated solar thermal technologies. Due to the high cost of lithium sulfate, we evaluated the potential of mixing lithium with sodium sulfate to create solid–solid cascaded PCM systems to provide higher thermal storage densities. We used differential scanning calorimetry, high-temperature in situ X-ray diffraction and thermogravimetric analysis to evaluate the phase-transition temperature, phase-change enthalpy, specific heat capacity, crystalline phase composition and thermal expansion. The obtained values for heat capacity and enthalpies of phase transitions showed good agreement with available thermodynamic databases. Therefore, further calculations of thermodynamic properties of each mixture in the system were performed for designing cascaded latent thermal energy storage system. From the PCM mixtures studied, NaLiSO4 shows the greatest stability under ambient conditions. A mixture of 59.17% NaLiSO4 and 40.83% Li2SO4 allows an optimum charge of both PCMs for power cycles such as supercritical CO2. Economic assessment revealed that this cascade system has an estimated cost of $50.2 kWhth−1.

First-principles calculations of phase transition, elasticity, phonon spectra, and thermodynamic properties for hafnium

In this work, structural transformation, elastic behaviors, phonon spectra, and thermodynamic properties upon hydrostatic compression of hafnium are investigated by using first-principle density functional theory. Our calculated equilibrium structural parameters and the transition pressures of α→ω→β are well consistent with experiments. At ambient pressure, the elastic constants indicate that the α and ω phases are mechanically stable while the β phase is unstable. The thermal properties including bulk modulus, entropy, and heat capacity in wide range of pressure and temperature for α-Hf are predicted. We present results of the phonon spectra and phonon density of states for the three experimentally observed phases and discuss the effects of pressure and temperature on those properties. The β-Hf is mechanically and dynamically stable at high pressure or at high temperature. Employing the quasiharmonic approximation as well as the Debye model, we calculate the Gibbs free energy and predict the pressure-temperature phase diagram.

First-principles study on stability, electronic, mechanical and thermodynamic properties of Al-Cu-RE ternary compounds

The crystal structure, phase stability, mechanical, electronic and thermodynamic properties of Al8Cu4RE compounds (RE = Y, Ce, Nd, Sm and Er) were investigated. The results of formation energies and elastic constants of compounds indicated that all Al8Cu4RE compounds were thermodynamically and mechanically stable. The calculated DOS of Al8Cu4RE were in good agreement with the results of formation energies. The elastic constants, bulk modulus, shear modulus, Young's modulus, G/B and Poisson's ratio of Al-Cu-RE compounds were also systematically calculated. The results showed that Al8Cu4RE compounds can be classified as brittleness material based on Pugh criteria and Poisson's ratio. And the calculations of thermodynamic properties indicated that the Debye temperature Al8Cu4Sm compound was significantly higher than that of others, which suggests that the lattice thermal conductivity of Al8Cu4Sm was the highest.

The Joule-Thomson Effect for Refrigerants with Dopants of the Fullerenes and Carbon Nanotubes

The importance of thermodynamic and phase behavior of working fluids embedded with nanostructured materials is fundamental to new nanotechnology applications. The fullerenes (C60) and carbon nanotubes (CNT) adding to refrigerants change their thermodynamic properties the Joule – Thomson effect such as dislocation of critical point, gas – liquid equilibria shift at alias. Algorithm of refrigerant thermodynamic property calculations based on the NIST (National Institute of Standards and Technologies) equation of state at different carbon nanotube concentrations is proposed. Thermodynamic properties of carbon dioxide in the C60 and CNT presence are given. Considering the extremely large number of different both nanoparticle types and reference fluids, it is obvious that there is need for developing theoretically sound methods of the prompt estimation thermodynamic properties and phase equilibria for emerging working media. The effect of nanoparticles on the critical point shift for classical fluids doped by nanoparticles is examined. The regular and singular parts of thermodynamic surface of reference fluid and nanofluid (volume nanoparticle concentration < 5%) are suggested to coincide in the reduced form. The shift of critical point for nanoliquids of industrial interest is theoretically predicted. Results of calculations of phase equilibria for some nanofluids are described.