Volume Thermal Expansion Coefficient Research Articles

High-pressure and high-temperature physical properties of LiF studied by density functional theory calculations and molecular dynamics simulations

Using the revised Perdew-Burke-Ernzerhof generalized gradient approximation based on first-principles plane-wave pseudopotential density functional theory, the high-pressure structural phase transition of LiF is explored. From the analysis of Gibbs free energies, we find that no phase transition occurs for LiF in the presented pressure range from 0 to 1000 GPa, and this result is consistent with the theoretical prediction obtained via ab initio calculations [N.A. Smirnov, Phys. Rev. B 83 (2011) 014109]. Using the classical molecular dynamics technique with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction, the melting phase diagram of LiF is determined. The obtained normalized volumes under pressure are in good agreement with our density functional theory results and the available experimental data. Meanwhile, with the help of the quasi-harmonic Debye model in which the phononic effects are considered, the thermodynamic properties of interest, including the volume thermal expansion coefficient, isothermal bulk modulus and its first and second pressure derivatives, heat capacity at constant volume, entropy, Debye temperature, and Grüneisen parameter of LiF are predicted systematically. All the properties of LiF with the stable NaCl-type structure in the temperature range of 0–4900 K and the pressure up to 1000 GPa are summarized.

Электронная структура и магнитный фазовый переход в геликоидальных ферромагнетиках Fe-=SUB=-1-x-=/SUB=-Co-=SUB=-x-=/SUB=-Si

AbstractLSDA + U + SO calculations of the electronic structure of helicoidal Fe_1 - x Co_ x Si ferromagnets within the virtual crystal approximation have been supplemented with the consideration of the Dzyaloshinski-Moriya interaction and ferromagnetic fluctuations of the spin density of collective d electrons with the Hubbard interactions at Fe and Co atoms randomly distributed over sites. The magnetic-state equation in the developed model describes helicoidal ferromagnetism and its disappearance accompanied by the occurrence of a maximum of uniform magnetic susceptibility at temperature T _ C and chiral fluctuations of the local magnetization at T > T _ C . The reasons why the magnetic contribution to the specific heat at the magnetic phase transition changes monotonically and the volume coefficient of thermal expansion (VCTE) at low temperatures is negative and has a wide minimum near T _ C have been investigated. It is shown that the VCTE changes sign when passing to the paramagnetic state (at temperature T _ S ).

High-temperature and high-pressure physical properties of CuI with zinc-blende phase by a systematic ab initio investigation

A systematic ab initio investigation has been performed to determine the elastic stability, the structural and finite-temperature thermodynamic properties of copper iodide (CuI) in the zinc-blende phase under pressure. All calculations are carried out based on the pseudopotential density functional method, in which we employ the generalized gradient approximation of the revised Perdew-Burke-Ernzerhof form and local density approximation of Ceperly and Adler parameterized by Perdew and Zunger together with plane-wave basis sets for expanding the periodic electron density. The obtained normalized volume dependence of the pressure and the equation-of-state parameters including equilibrium volume, isothermal bulk modulus and its pressure derivatives are in excellent agreement with the experimental data and other theoretical results. The elastic constants are calculated and the investigation of the mechanical stability from the elastic constants under pressure indicates that the zinc-blende CuI is stable up to 10GPa. Through the careful evaluation with the quasi-harmonic Debye model in which the phononic effects are considered, a complete set of thermodynamic data up to 800K, including the bulk modulus, volume thermal expansion coefficient, heat capacity, entropy, Debye temperature, and Grüneisen parameter of CuI with zinc-blende structure is achieved. This set of data is considered as the useful information to understand the high-temperature and high-pressure properties of CuI.

Hydrostatic pressure effects on the structural, elastic and thermodynamic properties of the complex transition metal hydrides A2OsH6 (A = Mg, Ca, Sr and Ba)

ABSTRACTWe report a systematic first-principles density functional theory study on the pressure dependence of the structural parameters, elastic constants and related properties and thermodynamic properties of the complex transition metal hydrides Mg2OsH6, Ca2OsH6, Sr2OsH6 and Ba2OsH6. The calculated structural parameters are in excellent agreement with the existing data in the scientific literature. The single-crystal elastic constants and related properties were predicted using the stress–strain method. The elastic moduli of the polycrystalline aggregates were evaluated via the Voigt–Reuss–Hill approach. The dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isobaric and isochoric heat capacity and Debye temperature on the pressure and temperature, ranging from 0 to 15 GPa and from 0 to 1000 K, respectively, were investigated using the quasi-harmonic Debye model in combination with first-principles calculations.

High-temperature thermodynamics of silver: Semi-empirical approach* *Project supported by the Major Research Project, UGC, New Delhi, India (Grant No. 42-771/2013 (SR)).

We report high-temperature thermodynamics for fcc silver by combining ab initio phonon dynamics to empirical quadratic temperature-dependent term for anharmonic part of Helmholtz free energy. The electronic free energy is added through an interpolation scheme, which connects ambient condition free electron gas model to Thomas–Fermi results. The present study shows good agreement with experimental and reported findings for several thermal properties, and the discrepancy observed in some caloric properties is addressed. The decreases in the product of volume thermal expansion coefficient and isothermal bulk modulus and in the constant volume anharmonic lattice specific heat at high temperature are the clear evidences of proper account of anharmonicity. The present study also reveals that T 2–dependent anharmonic free energy is sufficient for correct evaluation of thermal pressure and conventional Grüneisen parameter. We observe that the intrinsic phonon anharmonicity starts dominating above characteristic temperature, which is attributed to higher order anharmonicity and can be related to higher order potential derivatives. We conclude that the uncorrelated and largeamplitude lattice vibrations at high temperature raise dominating intrinsic thermal stress mechanism, which surpasses the phonon-anharmonism and requires future consideration.

Structural, mechanical, electronic and thermal properties of the newly predicted NB2 from ab initio calculations

The density functional theory (DFT) is used to investigate the structural, elastic, electronic and thermal properties of the newly predicted superhard material tetragonal NB2 (t-NB2). The estimated values of the elastic constants of this material satisfy its mechanical stability criteria. The calculated large values of bulk modulus (B), shear modulus (G), Young's modulus (E), Vickers hardness (Hv), and small Pugh's modulus and Poisson's ratio identify this compound as a potential candidate for superhard materials with high brittleness. The bulk modulus, Debye temperature, specific heats, and volume thermal expansion coefficient are also obtained as a function of temperature and pressure for the first time through the quasiharmonic Debye model with phononic effects. Large values of Debye and melting temperatures suggest the strong microhardness of t-NB2. The analysis of electronic density of states and Mulliken populations emphasizes the strong covalent bonding of B-B and B-N atoms which can be attributed to the mechanism of superhardness of t-NB2.

Phase transitions and thermal expansion of BaCO3 and SrCO3 up to 1413 K

The phase evolution and thermal expansivity of synthetic orthorhombic BaCO 3 (α-BaCO 3 ) and SrCO 3 (α-SrCO 3 ) were studied up to 1413 K using high-temperature powder X-ray diffraction. The α-BaCO 3 phase transformed into a trigonal β phase at 1073–1093 K with an increase in molar volume by 2.7%, and further to a cubic γ phase at 1233–1253 K with 0.2% increase in molar volume. The α-SrCO 3 phase transformed into a trigonal β phase at ∼1173 K. The fitted parameters for volume thermal expansion coefficients (α V ( T ) = a 0 (10 −5 K −1 ) + a 1 (10 −8 K −2 ) T ) are a 0 = 4.0(4), a 1 = 4.0(6) for α-SrCO 3 ; a 0 = 4.4(5), a 1 = 3.9(7) for α-BaCO 3 ; a 0 = 6.5(2) and a 0 = 6.8(1) for the β and γ phase of BaCO 3 , respectively. The β-BaCO 3 phase exhibits negative expansion along the a -axis, which may help to design new materials with tunable thermal behavior when it is mixed with materials with positive thermal expansion. The aragonite-group carbonates (CaCO 3 , SrCO 3 , and BaCO 3 ) have similar bulk thermal expansivity, but their anisotropy and linear expansivities vary with the size of the cation.

Study of some volumetric and refractive properties of {PEG 300 (1) + ethanol (2)} mixtures at several temperatures

ABSTRACTMolar volumes and excess molar volumes were investigated from measured density values for {PEG 300 (1) + ethanol (2)} binary mixtures at temperatures from 278.15 to 313.15 K. Both systems exhibit negative excess volumes probably due to increased interactions like hydrogen bonding and/or large differences in molar volumes of the components. Volume thermal expansion coefficients were also calculated for both binary mixtures and pure solvents. Refractive indices were also determined for all these non-aqueous mixtures and neat solvents at all temperatures. Furthermore, the Jouyban–Acree model was used for density, molar volume and refractive index correlations of the studied mixtures at different temperatures. The mean relative deviations between experimental and back-calculated density, molar volume and refractive index data were 0.07%, 0.99% and 0.01%, respectively.

Thermal behavior of mullite between 4 K and 1320 K

AbstractThe evolution of metric parameters of 2:1 and 3:2 mullites have been measured between 4 K and 1320 K using neutron and X‐ray powder diffraction. Negative thermal expansion was observed at low temperature for the a‐cell parameter and consequently for the cell‐volume, which is more pronounced for 2:1 mullite than those for 3:2 mullite. Each parameter is simulated using Grüneisen first‐order approximation for the zero pressure equation of state at 0 K, where the vibrational energy was calculated using microscopic approach. While the b‐ and c‐cell parameters require only one Debye term, a second Debye spectrum with negative Grüneisen parameter was required to fit the a‐cell parameter as well as the cell volume. At 4 K, 300 K and 1320 K the model, respectively, calculates the volume thermal expansion coefficients of 0.09x10−6 K−1, 9x10−6 K−1, and 17.3x10−6 K−1 for 2:1 mullite, and 0.09x10−6 K−1, 8.7x10−6 K−1, and 17.3x10−6 K−1 for 3:2 mullite. Temperature‐dependent Raman spectra and phonon density of states hint for the possible microscopic sources of the cell contraction at low temperature. A simple polynomial approach is presented to calculate the elastic stiffness coefficients of the 3:2 mullite, which are not available from experiments.

Influence of CaO/MgO ratio on the crystallization kinetics and interfacial compatibility with crofer 22APU and YSZ of strontium based alumino-borosilicate glasses for SOFC applications

High temperature hermetic sealants are required for the stability and good efficiency of the solid oxide fuel cells (SOFCs). Glass and glass ceramics are promising sealant materials due to their desirable properties and flexible compositions. In the present study, the novel glass series (10 + x) CaO-(10 − x) MgO-10SrO-10B2O3-20Al2O3-40SiO2 (x = 0, 2.5, 5, 7.5) has been synthesized via melt quenching route. These glass/glass ceramics are characterized by X-ray diffraction to evaluate the amorphous nature and phase formation, respectively. The activation energy has been analyzed by using three different theoretical models – Kissinger Model, Moynihan Model and Augis and Benett Model. In addition to this, the characteristic glass temperatures and coefficient of thermal expansion (CTE) have been obtained from DTA, differential DTA (DDTA) and Dilatometry. Various stability parameters like Hruby parameter, Saad Parameter, fluctuation free volume (fg) and bulk thermal expansion coefficient (αf) are also calculated with varying CaO/MgO ratio (R). Furthermore, to analyze the stability of the glasses with varying CaO/MgO ratio over a broader range of temperature, k parameters i.e. kb (T) and kf (T) are also evaluated for different heating rates. The diffusion couples of glasses with pre oxidized Crofer 22APU and YSZ fabricated at 850 °C for 500 h have been characterized using scanning electron microscopy (SEM) and X-ray dot mapping to investigate the sealing characteristics with varying CaO/MgO ratio. The glass series 15 CaMg is very stable and promises to be a good sealant for solid oxide fuel cells.

Investigation of thermodynamic stability, mechanical and electronic properties of superhard tetragonal B4CO4 compound: Ab initio calculations

The density functional theory (DFT) is employed to systematically investigate the structural, elastic, thermal properties, electronic structure and chemical bonding nature of the predicted superhard tetragonal B4CO4 (t-B4CO4). The estimated values of the elastic constants yield mechanical stability of this compound. The large values of bulk modulus (B), shear modulus (G), Young's modulus (E), Vickers hardness (Hv), small Pugh's modulus and Poisson's ratio identify this compound as a possible candidate for superhard material. The thermodynamic properties of t-B4CO4 are predicted for the first time through the quasi-harmonic Debye model where the lattice vibrations are taken into account. The variations of bulk modulus, Debye temperature, specific heats, and volume thermal expansion coefficient with temperature and pressure are successfully achieved for the first time. Predicted large values of Debye and melting temperatures anticipate the possibility of the strong microhardness of this compound. The analysis of electronic density of states and Mulliken populations emphasize the strong covalent bonding of BC (BO) atoms which can be attributed to the mechanism of superhardness of t-B4CO4.

Thermal Expansion Behavior of MI[AuX2(CN)2]-Based Coordination Polymers (M = Ag, Cu; X = CN, Cl, Br).

Two sets of trans-[AuX2(CN)2]--based coordination polymer materials-M[AuX2(CN)2] (M = Ag; X = Cl, Br or M = Cu; X = Br) and M[Au(CN)4] (M = Ag, Cu)-were synthesized and structurally characterized and their dielectric constants and thermal expansion behavior explored. The M[AuX2(CN)2] series crystallized in a tightly packed, mineral-like structure featuring 1-D trans-[AuX2(CN)2]--bridged chains interconnected via a series of intermolecular Au···X and M···X (M = Ag, Cu) interactions. The M[Au(CN)4] series adopted a 2-fold interpenetrated 3-D cyano-bound framework lacking any weak intermolecular interactions. Despite the tight packing and the presence of intermolecular interactions, these materials exhibited decreased thermal stability over unbound trans-[AuX2(CN)2]- in [nBu4N][AuX2(CN)2]. A significant dielectric constant of up to εr = 36 for Ag[AuCl2(CN)2] (1 kHz) and a lower εr = 9.6 (1 kHz) for Ag[Au(CN)4] were measured and interpreted in terms of their structures and composition. A systematic analysis of the thermal expansion properties of the M[AuX2(CN)2] series revealed a negative thermal expansion (NTE) component along the cyano-bridged chains with a thermal expansion coefficient (αCN) of -13.7(11), -14.3(5), and -11.36(18) ppm·K-1 for Ag[AuCl2(CN)2], Ag[AuBr2(CN)2], and Cu[AuBr2(CN)2], respectively. The Au···X and Ag···X interactions affect the thermal expansion similarly to metallophilic Au···Au interactions in M[Au(CN)2] and AuCN; replacing X = Cl with the larger Br atoms has a less significant effect. A similar analysis for the M[Au(CN)4] series (where the volume thermal expansion coefficient, αV, is 41(3) and 68.7(19) ppm·K-1 for M = Ag, Cu, respectively) underscored the significance of the effect of the atomic radius on the flexibility of the framework and, thus, the thermal expansion properties.

The thermal expansion and specific heat of solid oxide fuel cell cathode material Nd1-xSrxCoO3-δ

The thermal and allied properties of Nd1−xSrxCoO3-δ (0≤x≤0.8) were investigated in this work by means of Modified Rigid Ion Model (MRIM). Theoretically, MRIM provides arguably the most realistic interaction potential to treat these properties. We have computed the variation of specific heat and volume thermal expansion coefficient for these cobaltates. Here, Bulk modulus obtained from AIM theory is observed to be decreasing with increasing doping concentration x. The lattice specific heat is related to Debye temperature and hence this property shows a increasing trend with x and thermal expansion also follows the same increasing trend. The trend of variation of Debye temperature (θD), thermal expansion (α), bulk modulus (B) and cohesive energy (φ) with A-site cationic radius is predicted probably for the first time for these technologically important doped rare earth cobaltates.

Thermal expansion of the heavy-fermion superconductor PuCoGa5

We have performed high-resolution powder x-ray diffraction measurements on a sample of $^{242}$PuCoGa$_{5}$, the heavy-fermion superconductor with the highest critical temperature $T_{c}$ = 18.7 K. The results show that the tetragonal symmetry of its crystallographic lattice is preserved down to 2 K. Marginal evidence is obtained for an anomalous behaviour below $T_{c}$ of the $a$ and $c$ lattice parameters. The observed thermal expansion is isotropic down to 150 K, and becomes anisotropic for lower temperatures. This gives a $c/a$ ratio that decreases with increasing temperature to become almost constant above $\sim$150 K. The volume thermal expansion coefficient $\alpha_{V}$ has a jump at $T_{c}$, a factor $\sim$20 larger than the change predicted by the Ehrenfest relation for a second order phase transition. The volume expansion deviates from the curve expected for the conventional anharmonic behaviour described by a simple Gr\"{u}neisen-Einstein model. The observed differences are about ten times larger than the statistical error bars but are too small to be taken as an indication for the proximity of the system to a valence instability that is avoided by the superconducting state.

Structural, elastic and thermodynamic properties of iron carbide Fe7C3 phases: An ab initio study

Using ab initio spin-polarized density functional theory calculations, the structural, elastic and thermodynamic properties of the orthorhombic and hexagonal phases of the iron carbide Fe7C3 were investigated. The calculated ground-state lattice parameters are in good agreement with the available corresponding theoretical and experimental data. The single-crystal and polycrystalline aggregate elastic constants, sound velocities, Debye temperature, brittle/ductile character and elastic anisotropy have been estimated. The calculated bulk modulus values of both considered phases are very close and are approximately equal to 262GPa, which classifies the title compounds among the hard materials. The temperature and pressure dependencies of the unit-cell volume, bulk modulus, volume thermal expansion coefficient, isochoric and isobaric heat capacity, and Debye temperature were investigated using the quasi-harmonic Debye model.

Volumetric properties of {PEG 200 (or 300) (1) + water (2)} mixtures at several temperatures and correlation with the Jouyban–Acree model

ABSTRACTMolar volumes and excess molar volumes were investigated from density values for {PEG 200 (1) + water (2)} and {PEG 300 (1) + water (2)} binary mixtures at temperatures from 278.15 to 313.15 K. Both systems exhibit negative excess volumes probably due to increased interactions such as hydrogen bonding and/or large differences in molar volumes of components. Volume thermal expansion coefficients were also calculated for both binary mixtures and pure solvents. The Jouyban–Acree model was used for density and molar volume correlations of the studied mixtures at different temperatures. The mean relative deviations between experimental and calculated density data were 0.02% and 0.04%, for aqueous mixtures of PEG 200 and PEG 300, respectively; whereas the corresponding values for molar volume data were 1.76% and 2.72%.

The effect of alkyl chain length on material properties of fatty-acid-functionalized amidoamine-epoxy systems

Polyamine crosslinkers functionalized with pendant fatty acids are commercially used in epoxy coatings in part to enhance water barrier properties for corrosion prevention. However, a systematic understanding of the links between monomer molecular structure and material properties of such systems remains elusive, which limits our ability to design newer and more environmentally friendly coating systems. In this work, the effect of n-alkyl chain length in fatty-acid-functionalized polyamines on crosslinked epoxy-amidoamine systems is studied using a combined experimental and simulation-based approach. Both experiments and simulations show that density decreases and volume-expansion coefficients increase with increasing pendant chain length. Furthermore, it is shown that the trends in density and coefficient of volume thermal expansion with chain length obtained from simulations are consistent with an ideal mixing approximation. Interestingly, however, the glass-transition temperature Tg is found to be insensitive to chain length. Molecular simulations reveal that increasing the alkyl chain length from four to ten carbons does not introduce new flexibility mechanisms to the dense thermosets, which explains the Tg insensitivity. This work demonstrates a new way to significantly decrease the density of a thermoset polymer without compromising desirable properties such as high Tg and low coefficient of thermal expansion, and therefore may provide sounder rationale for molecular-based design of epoxy-based coatings.

Structure, thermal expansion and incompressibility of MgSO4·9H2O, its relationship to meridianiite (MgSO4·11H2O) and possible natural occurrences

Since being discovered initially in mixed-cation systems, a method of forming end-member MgSO4·9H2O has been found. We have obtained powder diffraction data from protonated analogues (using X-rays) and deuterated analogues (using neutrons) of this compound over a range of temperatures and pressures. From these data we have determined the crystal structure, including all hydrogen positions, the thermal expansion over the range 9–260 K at ambient pressure, the incompressibility over the range 0–1.1 GPa at 240 K and studied the transitions to other stable and metastable phases. MgSO4·9D2O is monoclinic, space group P21/c, Z = 4, with unit-cell parameters at 9 K, a = 6.72764 (6), b = 11.91154 (9), c = 14.6424 (1) Å, β = 95.2046 (7)° and V = 1168.55 (1) Å3. The structure consists of two symmetry-inequivalent Mg(D2O)6 octahedra on sites of \bar 1 symmetry. These are directly joined by a water–water hydrogen bond to form chains of octahedra parallel with the b axis at a = 0. Three interstitial water molecules bridge the Mg(D2O)6 octahedra to the SO4 2− tetrahedral oxyanion. These tetrahedra sit at a ≃ 0.5 and are linked by two of the three interstitial water molecules in a pentagonal motif to form ribbons parallel with b. The temperature dependences of the lattice parameters from 9 to 260 K have been fitted with a modified Einstein oscillator model, which was used to obtain the coefficients of the thermal expansion tensor. The volume thermal expansion coefficient, αV, is substantially larger than that of either MgSO4·7D2O (epsomite) or MgSO4·11D2O (meridianiite), being ∼ 110 × 10−6 K−1 at 240 K. Fitting to a Murnaghan integrated linear equation of state gave a zero-pressure bulk modulus for MgSO4·9D2O at 240 K, K 0 = 19.5 (3) GPa, with the first pressure derivative of the bulk modulus, K′ = 3.8 (4). The bulk modulus is virtually identical to meridianiite and only ∼ 14% smaller than that of epsomite. Above ∼ 1 GPa at 240 K the bulk modulus begins to decrease with pressure; this elastic softening may indicate a phase transition at a pressure above ∼ 2 GPa. Synthesis of MgSO4·9H2O from cation-pure aqueous solutions requires quench-freezing of small droplets, a situation that may be relevant to spraying of MgSO4-rich cryomagmas into the surface environments of icy satellites in the outer solar system. However, serendipitously, we obtained a mixture of MgSO4·9H2O, mirabilite (Na2SO4·10H2O) and ice by simply leaving a bottle of mid-winter brine from Spotted Lake (Mg/Na ratio = 3), British Columbia, in a domestic freezer for a few hours. This suggests that MgSO4·9H2O can occur naturally – albeit on a transient basis – in certain terrestrial and extraterrestrial environments.

A new method of preparing anhydrous magnesium carbonate (MgCO3) under high pressure and its thermal property

By using magnesium carbonate tri-hydrates (MgCO3·3H2O) as starting material, anhydrous magnesium carbonate (MgCO3) was successfully synthesized by dehydration method under high pressure for the first time. The property of as-synthesized sample was investigated by powder X-ray diffraction (XRD) and Raman spectroscopy, respectively. The high pressure synthesis was performed at the various conditions to ensure that the optimal condition is 3 GPa and 800 °C for 1 h, and it is reasonable to explain the principle of MgCO3 synthesis under high pressure. The size of micro-particles observed from Scanning Electron Microscope (SEM) image exceeds to 100 μm. As a good and important flame retardant material, its thermal property is investigated by Thermogravimetric (TG) analysis, Differential Scanning Calorimeter (DSC) measurement and high temperature X-ray diffraction (XRD) refinement, and the endothermic heat (128.59 KJ/mol), the thermal expansion coefficient along c-axis (αc = 1.639 × 10−5/°C), the thermal expansion coefficient along the a-axis (αa = 4.632 × 10−6/°C) and the volume thermal expansion coefficient (αV = 2.576 × 10−5/°C) was quantified.

Composition dependences of refractive index and thermo-optic coefficient in Ge-As-Se chalcogenide glasses

The refractive indices (n) and thermo-optic coefficients (ζ) of Ge14AsxSe86−x and GexAs12Se88−x glasses are measured in the 2–12μm mid-infrared range. The composition dependences of the two parameters are investigated and strategies for tailoring them are proposed. The density (d) shows a maximum at the stoichiometric composition when Ge content is fixed; while it exhibits a minimum at the mean coordination number (<r>) of 2.67 when As concentration is fixed. The volume thermal expansion coefficient (β) broadly decreases with increasing <r>. Two semi-empirical relations are used to predict n and ζ from the glass composition. The n of a Ge-As-Se glass could be predicted with an error of <1% from the d of the glass and the molar refractivity (Ri) of the constituent elements. The estimated values of Ri for Ge, As and Se between 2 and 12μm range from 10.12–10.52, 11.71–11.91, and 11.17–11.25cm3/mol, respectively. The ζ of a Ge-As-Se glass could be forecasted with an error of <6ppm/K from the β of the glass and the thermal coefficients of the molar refractivity (φi) of the constituent elements. The estimated values of φi for Ge, As and Se between 2 and 12μm range from 26.2–26.7, 54.9–55.7 and 85.4–86.8ppm/K, respectively.