Thermodynamic properties and phase stability of the Ba-Bi system: A combined computational and experimental study

An ab initio molecular dynamics exploration of associates in Ba-Bi liquid with strong ordering trends

“…The present AIMD results, as above stated, indicate that the Ba rich melt can be simplified as a mixture of liquid Ba and the connected BIPs, the Bi rich melt can be simplified as a mixture of liquid Bi and the connected BAPs. The findings of medium range ordering in the connected BIPs and the connected BAPs support the hypothesis of fictive associates used to model the Ba-Bi system [10].…”

“…The AIMD predicted enthalpy of mixing (Hmix) of molten Ba1-xBix at 1123 K ( Figure 1) agree well with the results by CALPHAD modeling using the associate model [10]. The enthalpy of formation (Hform) for the stable compounds predicted by DFT calculations at 300 K (using the GGA-PBE potential) [10] are also plotted in Figure 1. It is seen that Hform is close to the AIMD predicted Hmix, and there is a deep valley on the Hmix curve around the composition of compound Ba4Bi3, corresponding to the highest melting point in the Ba-Bi system, similarly to the Tl-Te [3], Pb-Te [6],…”

“…However, our computational results find that the mean Ba/Bi atomic ratios in the connected BIPs are roughly 8.05:1, 7.86:1, Figure 10). Therefore, it is reasonable to assign additional BaBi3 associate to describe Bi-rich melt, as proposed by Liu et al [10]. It is noted that this associate is weak ordering and poorly correlated to compound BaBi3.…”

“…In the associate model, the compositions of the associates are usually the same as those of the intermetallic compounds with high melting temperatures or highly negative values of enthalpy of mixing [3,4]. The associate model has been successfully applied to model thermodynamic properties of binary and multicomponent systems [2,3,[6][7][8][9][10][11][12].…”

“…In the associate model, the compositions of the associates are usually the same as those of the intermetallic compounds with high melting temperatures or highly negative values of enthalpy of mixing [3,4]. The associate model has been successfully applied to model thermodynamic properties of binary and multicomponent systems [2,3,[6][7][8][9][10][11][12].Atomic structures in molten or amorphous alloys are usually considered to be ordered in short up to medium range with the existence of hexagonal, pentagonal, and/or quadrangular bipyramid entities, such as in the molten Al [13], Ni [14], Zr [15], glass Zr80Pt20 [16], glass Al75Ni25 [16], and liquid/glass Cu-Zr [17]. Solute-solvent atomic network (e. g., in glass Ni63Nb37 [16] and liquid Ni3Al [18]) or connected pentagonal bi-pyramids (e.g., in molten Al3Cu[19]) can also form medium range orders (MRO).…”