Phase transition and thermodynamic properties of BaS: An Ab initio study

Abstract

The hydrostatic-pressure-induced transition phase of BaS from the NaCl-type structure (B1) to the CsCl-type structure (B2) is investigated by ab initio plane-wave pseudopotential density functional theory method. It is found that the transition pressure from B1 to B2 phases is 8.2 GPa according to the usual condition of equal enthalpy. Through the quasi-harmonic Debye model, the dependences of the relative volume V/V 0 on the pressure P, the thermal expansion parameter ratio 0 0 ( )/ γ γ γ − on pressure P, and the Debye temperature Θ and heat capacity C V on pressure P and temperature T are estimated.The high-pressure properties of II-VΙ compounds have attracted the interest of researchers for over 30 years because of their wide band gap character and the potential applications for optoelectronic devices [1,2] . However, only recently, the feasibility of green-blue opto-electronic devices based on these materials has been demonstrated [3] .BaS belongs to the family of alkaline-earth chalcogenides (XY: X= Be, Mg, Ca, Sr, Ba; Y=O, S, Se, Te), which can form a very important closed-shell ionic system crystallized in the six-fold coordinated NaCl-type (B1) structure or crystallize in eight-fold coordinated CsCl-type structure (B2) at room temperature [4] . The band gap ranges from about 2.5 to 6 eV. A noticeable feature in the electronic band structure of the XY compounds is that there is no d electron in the valance band. Previous experimental studies show that, prior to metallization, the barium chalcogenides BaY (Y=S, Se, Te) undergo phase transition from B1 to B2 structure at about 6.5, 6.0, and 4.8 GPa, respectively [4][5][6] .The structural and electronic properties of BaY (Y=O, S, Se, Te) compounds have been investigated, both experimentally [7] and theoretically during the past. In Ref.[8], local-density-functional total-energy calculations are reported for both the structural and metallization transitions of BaSe and BaTe. A metallization pressure of about 40 GPa is predicted for BaSe. These calculations represent the first convincing demonstration of the ability of the local-density-functional approximation to predict band-overlap metallization accurately [8] . The insulator-metal transition volumes for BaS, BaSe, and BaTe are calculated using the self-consistent augmented-

Extreme pressure conditions of bas based materials: Detailed study of structural changes, band gap engineering, elastic constants and mechanical properties

“…1c). Both BaS modifications were optimized using first principles calculations with LDA and GGA, and the results were in a very good agreement with previous experimental [17][18][19][20][21][22]24] and theoretical results [11,12,23,[25][26][27][28][29][30]47,48]. Since it has been observed that the calculated values of the cell parameters were slightly underestimated compared to the experimental values, while the GGA-PBE functional slightly overestimates (see supporting information, Table S1), each of the investigated properties in this study were calculated with both LDA and GGA approaches for comparison.…”

“…There has been extensive theoretical work published on barium sulphide in the literature, mostly because of opto-electrical applications of barium chalcogenides. Most of these researches are focusing on the phase transitions, band structure, density of states (DOS), thermodynamic and elastic properties of well-known NaCl and CsCl modifications at standard conditions [25][26][27][28][29][30][31][32].…”

First principles study of the structural, mechanical, phonon, optical, and thermodynamic properties of half-Heusler (HH) compound NbFeSb

“…Grüneisen parameter γ is another important thermodynamic quantity which is thought to be described as the alteration in a frequency of the crystal lattice vibration based on the lattice's increase or decrease in volume as the temperature changes [48]. The Grüneisen parameter of cubic NbFeSb is presented in figure 9 under various pressures and temperatures.…”

Operation safety evaluation system of ship lock based on extension evaluation and combination weighting method

“…These research results have played an important role in promoting the safety evaluation of ship lock operation, but due to many factors affecting the safety of ship lock operation and the work to be done, there is no relevant and complete safety evaluation system around the world (Teng 2011).…”