Thermodynamic modelling of the general NiAs-type structure: A study of first principle energies of formation for binary Ni-containing B8 compounds

Thermodynamic assessment of the Ni–Te system

“…The formation enthalpy by Jandl et al is very close to the calorimetric data point of a NiTe sample by Predel and Ruge [33], whose analyzed composition corresponds to a two-phase equilibrium of d þ c1: Figure 3 shows the calculated enthalpy of formation, separately calculated, for all phases in the system. The enthalpy of the b2 phase closer fits DFT values than the experimental data point, while the d phase has a lower enthalpy than predicted by DFT at the NiTe end-member [34]. Therefore, the c1 phase has a lower enthalpy than predicted by DFT in order to lie on a line in Gibbs energy between b2 and d: Figure 4 shows the calculated heat capacity of b2 compared with experimental data of 40 at.% Te and 41.1 at.% Te [28].…”

“…Heat capacity has been measured on the b2 and d phases by several authors in a cryostat [27], via adiabatic shield calorimetry (AShC) [28,29], differential scanning calorimetry (DSC) [30] and adiabatic scanning calorimetry (AScC) [31]; they are all consistent, and the b2 phase measurements show several lambda-type transitions. Enthalpy of formation has only been measured by solution calorimetry on the b2 phase by Shukla et al [32], and supposedly on d by Predel and Ruge [33], although their composition corresponds to c1 þ d. Jandl et al [34] evaluated 0 K formation enthalpies of the d phase by DFT calculations. Activity data have been collected on most phases of the system via isopiestic measurements [14], Knudsen effusion mass spectrometry (KEMS) [35,36] and electromotive force (EMF) [21,[37][38][39].…”

“…FCC þ b1 eutecticum and activity data [14,35,36,39] All terms except the entropy terms (bT in Eq. 6) of the dÀNiTe and d À NiTe 2 end-members were fitted to the formation enthalpy data evaluated via DFT by Jandl et al [34] and the heat capacity data of Grønvold [29] and Tsuji and Ishida [31]. The interaction terms were then optimized to fit activity data [14,21,38] and the bT terms to fit solidus data [14,15] and the phase boundaries evaluated by Barstad et al [13].…”

Thermodynamic assessment of the Fe-Te system. Part II: Thermodynamic modeling

“…The formation energies of the end-members (Table 3) of the , , , and phases are summarized in Table 4 together with converged parameters. In phases of the NiAs-type structure, here and , some atoms may be interstitially dissolved in the trigonal-bipyramidal holes [31]. In order to test the possibility of Fe atoms occupying those sites, the formation energy of the end-member -, i.e.…”

“…The third sublattice, which is optional -and hereafter omitted -may be added to accommodate for the possibility of including interstitial atoms in the trigonal-bipyramidal sites, as is possible e.g. with Sn in the Ni-Sn-Te system, among others [31].…”