Melting temperature prediction by thermoelastic instability: An ab initio modelling, for periclase (MgO). (June 2021)

• Record Type: Journal Article
• Authors: Merli, Marcello; Pavese, Alessandro
• Is Part Of: Calphad. Volume 73(2021)
• Publication Date: 2021-06
• Subjects: Melting temperature -- Thermo-elastic instability -- Catastrophe theory -- Ab-initio modelling -- Periclase (MgO); Phase diagrams -- Data processing -- Periodicals; Thermochemistry -- Data processing -- Periodicals; Diagrammes de phases -- Informatique -- Périodiques; Thermochimie -- Informatique -- Périodiques; Thermodynamica; Electronic journals; 541.363
• DOI: 10.1016/j.calphad.2021.102259
• Languages: English
• ISSNs: 0364-5916

Abstract

Abstract: Melting temperature ( T M ) is a crucial physical property of solids and plays an important role for the characterization of materials, allowing us to understand their behavior at non-ambient conditions. The present investigation aims i) to provide a physically sound basis to the estimation of T M through a "critical temperature" ( T C ), which signals the onset of thermodynamic instability due to a change of the isothermal bulk modulus from positive to negative at a given P C - V C - T C point, such that (∂ P /∂ V ) V C, T C = -(∂ 2 F /∂ V 2 ) V C, T C = 0; ii) to discuss the case of periclase (MgO), for which accurate melting temperature observations as a function of pressure are available. Using first principles calculations, quasi-harmonic approximation and anharmonic correction, we model the Helmholtz potential, i.e . F ( V, T ), and determine pressure thereby. A comparison between measured and predicted T M values as a function of pressure shows achievement of an average discrepancy of ~2.9%, in the range 0–25 GPa and 3000–5000 K.