Interatomic Potential Method Research Articles

Dissolution of impurities in sodium gadolinium molybdate NaGd(MoO<sub>4</sub>)<sub>2</sub>

Impurity defects simulation in sodium-gadolinium molybdate NaGd(MoO4)2 was carried out using a method of interatomic potentials. The dissolution energies of tri-, di- and monovalent impurities were estimated. The dependences of the dissolution energy on the ionic radius of the impurity were plotted. For heterovalent substitutions, the most energetically favorable mechanism for charge compensation has been found, both due to intrinsic crystal defects and according to the conjugate isomorphism scheme. The positions of the most probable localization of defects are determined. The effect of disordering of sodium and gadolinium ions at equivalent positions on positional differences in the energy of defects is estimated. A comparison of the solubility of impurities in NaGd(MoO4)2 and its isostructural CaMoO4 indicates that, although isovalent substitutions are energetically more favorable than heterovalent ones, the mechanism of conjugate isomorphism, which ensures electrical neutrality, can equalize these processes.

Experimental and Computational Study Toward Identifying Active Sites of Supported SnOx Nanoparticles for Electrochemical CO2 Reduction Using Machine-Learned Interatomic Potentials.

SnOx has received great attention as an electrocatalyst for CO2 reduction reaction (CO2RR), however; it still suffers from low activity. Moreover, the atomic-level SnOx structure and the nature of the active sites are still ambiguous due to the dynamism of surface structure and difficulty in structure characterization under electrochemical conditions. Herein, CO2RR performance is enhanced by supporting SnO2 nanoparticles on two common supports, vulcan carbon and TiO2. Then, electrolysis of CO2 at various temperatures in a neutral electrolyte reveals that the application window for this catalyst is between 12 and 30°C. Furthermore, this study introduces a machine learning interatomic potential method for the atomistic simulation to investigate SnO2 reduction and establish a correlation between SnOx structures and their CO2RR performance. In addition, selectivity is analyzed computationally with density functional theory simulations to identify the key differences between the binding energies of *H and *CO2 -, where both are correlated with the presence of oxygen on the nanoparticle surface. This study offers in-depth insights into the rational design and application of SnOx-based electrocatalysts for CO2RR.

Giant thermal conductivity and strain thermal response of nitrogen substituted diamane: a machine-learning-based prediction.

With the ongoing trend of seeking miniaturization and enhanced performance for electronic devices, effective thermal management has emerged as a critical concern. The discovery and investigation of high thermal conductivity (κ) materials have proved to be pivotal in addressing this challenge. This study aims to explore the distinctive properties and potential applications of nitrogen substituted diamane (NCCN), a two-dimensional material with a diamond-like structure composed of carbon and nitrogen atoms. This work systematically delves into NCCN's thermal, mechanical, and electrical properties. It is predicted that NCCN exhibits an exceptional κ, ∼2288 W m-1 K-1, at room temperature (300 K) by combining the machine-learning interatomic potential method and the phonon Boltzmann transport equation, surpassing that of H-diamane and rivaling that of diamond, and an impressive electronic band gap of ∼4.47 eV (PBE). For mechanical properties, the stress-strain relationship reveals that NCCN exhibits isotropic elastic properties and anisotropic tensile strengths. Additionally, the variations in NCCN's κ and electronic energy band structure under different strains underscore its substantial potential in the field of thermoelectric applications.

Oxide Ion Conduction in Ca-Doped Yb3Ga5O12 Garnet.

Developing oxide ion conductors with new structural families is important for many energy conversion and storage techniques. Herein, a series of Ca-doped Yb3Ga5O12 garnet-type materials are prepared through a traditional solid-state reaction method, with their oxide ion conduction properties being reported for the first time. The results revealed that Ca substitution for Yb would significantly improve the conductivity of Yb3Ga5O12 from 3.57 × 10-7 S/cm at 900 °C under air to 1.66 × 10-4 S/cm, with an oxide ion transporting number of ∼0.52. The oxygen vacancy defect formation energy (∼0.127 eV) and the local structure around an oxygen vacancy were studied by atomic-level static lattice simulations based on the interatomic potential method. The oxide ion conducting mechanism was studied by the bond-valence-based method, which revealed three-dimensional pathways for oxide ion migration in both the parent and Ca-doped structures. The simulated activation energy of oxide ion migration decreased slightly from ∼0.358 eV in the parent structure to 0.346 eV in the doped one. These discoveries in the Ca-doped Yb3Ga5O12 will stimulate extensive exploitation and fundamental research on garnet-type materials.

Dissolution Energies of Impurities and Their Clusters in Powellite CaMoO4

The impurity defects in CaMoO4 are simulated by the method of interatomic potentials. The dissolution energies of monovalent, divalent, and trivalent impurities are calculated, their comparative analysis is performed, and the main patterns of change are presented. The most probable localization of defects is determined. In the case of heterovalent impurities, the most energetically favorable mechanism for their charge compensation has been found, both due to intrinsic crystal defects and under conjugate isomorphism. It is shown that the formation of impurity clusters with intrinsic crystal defects and (to a greater extent) the formation of clusters of different-valence impurities may significantly reduce the dissolution energy of impurities. The formation of neutral clusters of univalent impurities with oxygen vacancies not only makes it possible to increase the solubility of impurities but also reduces the probability of the formation of color centers.

CaMoO-=SUB=-4-=/SUB=--NaGd(MoO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=- Solid Solutions: simulation of properties and local structure by the method of interatomic potentials

Simulation of CaMoO4-NaGd(MoO4)2 solid solutions by the method of interatomic potentials is carried out. It is shown that solid solutions exist in the entire range of compositions and are close to ideal. Dependences on the composition of the lattice parameters and volume of the unit cell, density, bulk modulus, enthalpy, vibrational entropy and heat capacity are obtained. Temperature dependences of heat capacity and vibrational entropy are constructed. Analysis of the local structure and its changes depending on the composition of the Ca1-xNax/2Gdx/2MoO4 solid solution showed that in solid solution the interatomic distances of Gd-O are on average 2.62% less, and Na-O is 3.15% greater than the distances of Ca-O. In general, this leads to an increase in the lattice parameters and volume of the unit cell during the formation of Ca1-xNax/2Gdx/2MoO4 solid solutions compared to CaMoO4. Keywords: simulation, molybdates, the solid solutions, local structure.

MD simulation of interactions of atomic displacement cascades with β-Nb precipitates in a zirconium matrix

In this work, we investigated the effect of spherical binary precipitates and needle-shaped nanoparticles of β-Nb on the evolution of cascade processes in the Zr matrix using the method of molecular dynamics and many-body interatomic potentials. For a case of spherical precipitates, the formation of the interphase region with length of ~ 10 Å was observed. The fraction of the Zr atoms in the precipitate increased during the cascade processes. The Nb atoms, which were initially inside the precipitate, did not leave the boundaries of the interphase region after relaxation of the model crystallite. After the cascade process, the Nb atoms were detected Zr matrix at a distance of no more than 5 Å from interphase boundary. Point defects, as well as their clusters, are formed mainly near the surface of the precipitate. In a case of needle-shaped nanoparticles, a slight “blurring” of the particle boundaries with an increase in the number of niobium atoms in the near- boundary region were observed. After the atomic displacement cascade, part of the niobium atoms moved from nanoparticle into the near-boundary region. Only a few niobium atoms moved into the α-phase matrix outside the near-boundary region. No cases of significant dissolution of the nanoparticle were observed. We also observed the formation of clusters consisting of a mixture of vacancies and SIAs in the structure of the nanoparticle.

In-depth lithium transportation mechanism and lithium intercalation study of BaLi2Ti6O14 anode material by atomistic simulations

Abstract Atomistic simulations based on pedone interatomic potential model and first principle method are applied to observe the concerted motion of lithium ions in the lattice of BaLi2Ti6O14 anode material. The superimposed Li+ trajectory at all timeframes offers an intuitive, reliable image of the Li+ migration mechanism in crystal lattice. It reveals three possible Li+ migration paths, that is, 16 g Li-8e/8c interstitial octahedral site −16 g Li along c direction, 16 g Li- empty 8f/4b- 16 g Li along a direction and Ti3/Ti4 mediated hopping along b axis realized by Ti-Li disordering. The site displacement function (SDF) analysis shows that Ti-Li exchange does not happen for most of the simulation time. Mean square displacement (MSD) of the Li+ motion gives the energy barrier value of three migration modes and accordingly, the extrapolated diffusion coefficients at room temperature. These results show that the Li+ transportation along c-axis and a-axis are the dominant Li+ migration routes for BaLi2Ti6O14 material. 7 intermediate phases are determined according to the formation energy curve and the voltage profile is predicted accurately accordingly. Also, the state of the charge (SOC) dependency of the lithium vitality shows that upon the initiation of the lithium ion intercalation, the lithium ion diffusion coefficient soars quickly, reaches the maximum at x = 1 and then fluctuates in a small range (1.6 × 10−10 −2.9 × 10−9 cm2·s−1).

Transferable Approach of Semi-Empirical Modeling of Disordered Mixed-Halide Hybrid Perovskites CH3NH3Pb(I1–xBrx)3: Prediction of Thermodynamic Properties, Phase Stability, and Deviations from Vegard’s Law

We report here a novel approach on computational investigation of the CH3NH3Pb(I1–xBrx)3 solid solutions using the classical interatomic potential method in disorder supercells. The developed interatomic potential set is used to calculate Gibbs free energy and geometrical parameters for orthorhombic, tetragonal and cubic modifications of perovskites with various I/Br ratio at different temperatures. The obtained results are in a good agreement with experimental data and predict a tetragonal to cubic phase transition at Br content of ∼0.2 and experimentally observed deviation from the Vegard’s law for the CH3NH3Pb(I1–xBrx)3 disordered solid solution. In addition, we calculated thermal dependency of Gibbs free energy and therefore provided a thermodynamic rationale for a large miscibility gap in orthorhombic and tetragonal modifications of CH3NH3Pb(I1–xBrx)3 at low temperatures. This, in turn, provides thermodynamic driving force for phase segregation of the mixed-halide perovskites, which was proved experi...

Investigation of Li Ion Dynamics in Garnet Oxide Li6.5La3Zr1.5Ta0.5O12 Using Molecular Dynamics Simulation

To overcome the safety issue of liquid electrolytes in conventional lithium-ion batteries, various solid-state inorganic electrolytes have been studied. Among them, lithium garnet oxides have been attracting research interests due to their high ionic conductivity, Li7-xLa3Zr2-xTaxO12 (LLZTO) with have a at room temperature with a maximum value around x = 0.51,2. There are two different structures of lithium garnet oxides, a cubic structure with space group Iad and a tetragonal phase with space group I41/acd. The cubic structure has two types of Li sites, i.e., tetrahedral (Td) 24d sites and octahedral (Oh) 48g sites. The tetragonal structure has four types of Li sites, i.e., Td-8a, Td-16e, Oh-16f, and Oh-32g sites. The fully empty 16e sites and fully occupied the other sites in tetragonal structure makes its conductivity about 2 orders lower than the cubic phase. However, the complexity of structure hindered the understanding of the mechanism of lithium ion conduction. In this paper, we performed molecular dynamics (MD) simulation on Li6.5La3ZrTaO12 based on classic MD simulation from both the interatomic potential and DFTB methods to study its structure and properties including lattice parameters, diffusion parameters, ionic conductivities, dielectric constants, and elastic moduli. The results are extracted through correlation function that was used for simple liquids3. The consistency of our results with the reported experimental ones helped us to understand the Li diffusion mechanism. References (1) Y. X. Wang and W. Lai "High Ionic Conductivity Lithium Garnet Oxides of Li7-xLa3Zr2-xTaxO12 Compositions," Electrochem. Solid State Lett. 2012, 15, A68-A71. http://dx.doi.org/10.1149/2.024205esl(2) Y. T. Li, J. T. Han, C. A. Wang, H. Xie, and J. B. Goodenough "Optimizing Li+ conductivity in a garnet framework," J. Mater. Chem. 2012, 22, 15357-15361. http://dx.doi.org/10.1039/c2jm31413d(3) In Theory of Simple Liquids (Fourth Edition); J.-P. Hansen and I. R. McDonald, Eds.; Academic Press: Oxford, 2013, p i.

Simulation of the NaGd(MoO4)2–NaEu(MoO4)2 and Na2Gd4(MoO4)7–Na2Eu4(MoO4)7 Solid Solutions by the Interatomic Potential Method

Simulation of the solid solutions in the system of double sodium–gadolinium and sodium–europium molybdates, which are promising matrices for solid state lasers and phosphors has been carried out by the method of interatomic potentials. Two types of solid solutions have been studied, one of which contains finite components corresponding to the stoichiometric NaGd(MoO4)2–NaEu(MoO4)2 compositions with statistical distribution of cations in the crystal lattice. Another object is a cation-deficient Na2Gd4(MoO4)7–Na2Eu4(MoO4)7 system, in which we have examined the variants of statistical distribution and partial ordering of cations over structural positions. Atomistic simulation has been performed using the GULP 4.0.1 software package (General Utility Lattice Program). It is shown that when we pass from sodium-gadolinium molybdate to sodium-europium molybdate, both of stoichiometric and cation-deficient compositions, an increase in the unit cell volume is observed, while the density of the crystal, the energy of interatomic interactions in the structure, the vibrational entropy and the heat capacity decrease along with increasing europium content. The energy of interatomic interactions in the structure for cation-deficient solid solutions is less than for stoichiometric ones. Other aforementioned characteristics for cation-deficient solid solutions have greater values than for stoichiometric ones. The role of cluster europium centers in concentration quenching in NaGd(MoO4)2–NaEu(MoO4)2 solid solutions has been examined.

Моделирование твердых растворов NaGd(MoO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=-- NaEu(MoO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=- и Na-=SUB=-2-=/SUB=-Gd-=SUB=-4-=/SUB=-(MoO-=SUB=-4-=/SUB=-)-=SUB=-7-=/SUB=--Na-=SUB=-2-=/SUB=-Eu-=SUB=-4-=/SUB=-(MoO-=SUB=-4-=/SUB=-)-=SUB=-7-=/SUB=- методом межатомных потенциалов

AbstractSimulation of the solid solutions in the system of double sodium–gadolinium and sodium–europium molybdates, which are promising matrices for solid state lasers and phosphors has been carried out by the method of interatomic potentials. Two types of solid solutions have been studied, one of which contains finite components corresponding to the stoichiometric NaGd(MoO_4)_2–NaEu(MoO_4)_2 compositions with statistical distribution of cations in the crystal lattice. Another object is a cation-deficient Na_2Gd_4(MoO_4)_7–Na_2Eu_4(MoO_4)_7 system, in which we have examined the variants of statistical distribution and partial ordering of cations over structural positions. Atomistic simulation has been performed using the GULP 4.0.1 software package (General Utility Lattice Program). It is shown that when we pass from sodium-gadolinium molybdate to sodium-europium molybdate, both of stoichiometric and cation-deficient compositions, an increase in the unit cell volume is observed, while the density of the crystal, the energy of interatomic interactions in the structure, the vibrational entropy and the heat capacity decrease along with increasing europium content. The energy of interatomic interactions in the structure for cation-deficient solid solutions is less than for stoichiometric ones. Other aforementioned characteristics for cation-deficient solid solutions have greater values than for stoichiometric ones. The role of cluster europium centers in concentration quenching in NaGd(MoO_4)_2–NaEu(MoO_4)_2 solid solutions has been examined.

Simulation of Simple and Complex Gadolinium Molybdates by the Interatomic Potential Method

Crystals of ferroelectric‒ferroelastic gadolinium molybdate Gd2(MoO4)3, calcium molybdate CaMoO4, and double sodium‒gadolinium molybdates of stoichiometric (Na1/2Gd1/2MoO4) and cationdeficient (Na2/7Gd4/7MoO4) compositions, which are used to design solid-state lasers, phosphors, and white LEDs, have been simulated by the interatomic potential method. Their structural, mechanical, and thermodynamic properties are calculated using a unified system of interatomic potentials and effective ion charges, which demonstrated transferability and made it possible not only to describe the existing experimental data but also to predict some important physical and thermodynamic properties of molybdate crystals. The influence of the deviation from stoichiometry and partial ordering of cations on sites in nonstoichiometric crystals on the properties and local structure of sodium‒gadolinium molybdates is discussed.

Effects of interatomic potential on precipitation sequences of medium Al concentration in Ni<sub>75</sub>Al<sub><i>x</i></sub>V<sub>25-<i>x</i></sub> alloys

The study of material properties show that there is a large space and time span from the electronic level, atomic level, to molecules, clusters, mesoscopic to macroscopic continuous medium. Different levels are dealt with by using different research methods. The interatomic potential function method is an important intermediary bridging from atomic level to cluster and mesoscopic physics research. Therefore, it is not only for a research field of condensed matter physics, but also for an interdisciplinary research. The interatomic potential, as the basis of all computer simulations at an atomic level, directly affects the accuracy of simulation results. That is to say, it is a greatly significant to study the interatomic potential at the atomic level. This article is based on the inversion algorithm and microscopic phase field, and the influence of medium Al concentration and temperature on the precipitation process of Ni<sub>75</sub>Al<sub><i>x</i></sub>V<sub>25-<i>x</i></sub> alloy are studied. At the same concentration, the first nearest neighbor interatomic potential of L1<sub>2</sub> and DO<sub>22</sub> phase increase linearly with increasing temperature, which is proportional to each other. However, the first nearest neighbor interatomic potential for L1<sub>2</sub> (DO<sub>22</sub>) phase increases (decreases) with the increase of Al atom concentration at a constant temperature. When the temperature is 1046.5 K and the concentration of Al is 0.06, the interatomic potential of L1<sub>2</sub> phase is consistent with the first principles calculation by Chen, indicating the reliability of the inversion algorithm. At the same time, the inverse interatomic potentials are taken into consideration in the microscopic phase field simulation to investigate the relationship between the precipitation sequence of the medium Al alloy and the interaction potential between atoms. That is to say, when the first neighbor interatomic potential of L1<sub>2</sub> is greater than (less than DO<sub>22</sub>) L1<sub>2</sub> (DO<sub>22</sub>) precipitated preferentially. The first nearest neighbor interatomic potential for L1<sub>2</sub> and DO<sub>22</sub> are equal, both of which are precipitated at the same time. In particular, when the concentration of Al atoms is equal to 0.0589, it is found that L1<sub>2</sub> and DO<sub>22</sub> are simultaneously precipitated. The precipitation mechanism of the alloy with medium Al concentration is a hybrid mechanism with both non-classical nucleation and instability decomposition characteristics. Since the precipitation mechanism of the medium-concentrated alloy is a hybrid mechanism with both non-classical nucleation and spinodal decomposition, the microscopic phase field method is used to invert the interatomic potential, which increases the reliability of the precipitation sequence of medium the Al alloy.

Dimer self-organization of impurity ytterbium ions in synthetic forsterite single crystals

Paramagnetic centers formed by impurity Yb3+ ions in synthetic forsterite (Mg2SiO4) grown by the Czochralski technique are studied by X-band CW and pulsed EPR spectroscopy. These centers are single ions substituting magnesium in two different crystallographic positions denoted М1 and М2, and dimer associates formed by two Yb3+ ions in nearby positions М1. It is established that there is a pronounced mechanism favoring self-organization of ytterbium ions in dimer associates during the crystal growth, and the mechanism of the spin–spin coupling between ytterbium ions in the associate has predominantly a dipole–dipole character, which makes it possible to control the energy of the spin–spin interaction by changing the orientation of the external magnetic field. The structural computer simulation of cluster ytterbium centers in forsterite crystals is carried out by the method of interatomic potentials using the GULP 4.0.1 code (General Utility Lattice Program). It is established that the formation of dimer associates in the form of a chain parallel to the crystallographic axis consisting of two ytterbium ions with a magnesium vacancy between them is the most energetically favorable for ytterbium ions substituting magnesium in the position М1.

Atomistic simulation of ferroelectric–ferroelastic gadolinium molybdate

Gadolinium molybdate Gd2(MoO4)3 orthorhombic ferroelectric ferroelastic (β'-phase) is simulated by the method of interatomic potentials. The simulation is performed using the GULP 4.0.1 code (General Utility Lattice Program), which is based on the minimization of the energy of the crystal structure. Parameters of the gadolinium–oxygen interatomic interaction potentials are determined by fitting to the experimental structural data and elastic constants by a procedure available in the GULP code. Atomistic modeling using the effective atomic charges and the system of interatomic potentials made it possible to obtain reasonable estimates of structural parameters, atomic coordinates, and the most important physical, mechanical, and thermodynamic properties of these crystals. Temperature dependences of the heat capacity and vibrational entropy of the crystal are obtained. The calculated parameters of gadolinium–oxygen interaction potentials can be used to simulate more complex gadolinium-containing compounds.

Atomistic simulation of sodium–gadolinium molybdate of stoichiometric (Na1/2Gd1/2MoO4) and cation-deficient (Na2/7Gd4/7MoO4) compositions

Crystals of sodium–gadolinium molybdates of two compositions: stoichiometric (Na1/2Gd1/2MoO4) and cation-deficient (Na2/7Gd4/7MoO4) composition in which 1/7 of the corresponding cation positions are not occupied are simulated by the method of interatomic potentials. For cation-deficient crystals, two kinds of cation position distribution are considered: the statistical distribution of sodium, gadolinium, and unoccupied cation positions in the I41/a structure and their partial ordering in the I space group. As a result of the simulation, structural characteristics of sodium–gadolinium molybdates agreeing well with the known experimental data are obtained. In addition, a number of important elastic and thermodynamic properties of these compounds are predicted. The results obtained in the partial-occupancy approximation and by constructing a 7 × 2 × 2 supercell are compared. The local structure of sodium–gadolinium molybdates are analyzed in detail. The influence of the deviation from the stoichiometry as well as cation ordering on the properties of these crystals is discussed.

CT-MEAM interatomic potential of the Li-Ni-O ternary system for Li-ion battery cathode materials

Conventional interatomic potential methods for Li-ion battery cathode materials normally use fixed-charge models, which are not accurate enough to model the dynamical oxidation state change of transition metals during electrochemical reactions. In order to enable more accurate large-scale simulations for battery cathode materials, here we report a semiempirical interatomic potential of the Li-Ni-O ternary system based on an advanced dynamic charge method: Charge-Transfer Modified Embedded-Atom Method (CT-MEAM). The potential is parameterized by fitting the atomic Bader charges and energy-strain curves of the LiNiO2 cathode material under uniaxial, biaxial and hydrostatic strains to results obtained with ab initio density-functional theory (DFT) calculations. A variety of structural, electrochemical and dynamical properties derived from the fitted CT-MEAM potential are observed to be in excellent agreement with previous DFT and experimental data. The transferability of the potential is validated by comparing relative phase stabilities and charge distribution states within the ternary Li-Ni-O systems. Our results support the capability of the present CT-MEAM to model complex ternary transition metal oxides. This method will facilitate not only the optimal design of Lithium-ion battery cathode materials, but also other transition metal oxide-based applications involving electrochemical reactions.

Simulation of the local structure, properties of mixing, and stability of solid solutions Ba x Sr1–x CO3 by the interatomic potential method

The strontianite (SrCO3)–witherite (BaCO3) solid solutions have been simulated using the interatomic potential method. The dependences of the unit cell parameters, the unit cell volume, and the bulk modulus on the composition of the solid solution have been constructed. It has been shown that the unit cell volume and the bulk modulus exhibit negative deviations from the additivity. An analysis of the local structure of the solid solutions has been carried out. It has been found that, for the equimolar composition of the BaxSr1–xCO3 solid solution, the relaxations of the barium and strontium positions are equal to 60 and 56%, respectively. It has been established that the enthalpy of mixing is positive and, for the equimolar composition of the solid solution, reaches a maximum value of 3.4 kJ/mol. The obtained results have been compared with the experimental data. The solvus of the BaxSr1–xCO3 system has been constructed based on the dependences of the Gibbs free energy on the composition in the temperature range from 300 to 1000 K.

Simulation of the local structure, mixing properties, and stability of Ca x Sr1 − x CO3 solid solutions by the interatomic potential method

Strontianite (SrCO3)-aragonite (CaCO3) solid solutions have been simulated by the interatomic potential method. The composition dependences of the unit cell parameters, the unit cell volume, and bulk modulus have been constructed. It has been shown that the volume of the unit cell and bulk modulus show small negative deviations from additivity. The local structure of solid solutions has been analyzed. It has been established that the enthalpy of mixing is positive and, for the equimolar composition, reaches a maximum of 2.45 kJ/mol. Based on the composition dependences of the Gibbs free energy for the temperature range of 300–650 K, the solvus of the system has been constructed. According to the obtained data, the solubility of aragonite in strontianite under ambient conditions is 5.5 mol %, while that of strontianite in aragonite is 2.8 mol %. The miscibility gap of the system disappears at around 450 K. The calculated results have been compared with the experimental data.