What is the purpose of the phase B2_BCC!BCC_A2 in the SGTE (SGSLsoln) solution database?
For the body centered cubic structure (BCC) there is a disordered state in which atoms randomly occupy the sites, and there is an ordered state with preferential occupation of the sites. For the Fe-Al (and Fe-Si) system the transition of the disordered (Fe-rich) state into the ordered state at high Al- (and Si-) content has been modelled such that the Gibbs free energy of the disordered state (BCC_A2) is taken as the basis of the calculation and the ordering energy for B2_BCC is added as an extra but necessary contribution. Such a case is denoted by the by the full name B2_BCC!BCC_A2. This means that whenever B2_BCC is selected for a calculation, BCC_A2 is also selected automatically by the program (but not visa versa). Since B2_BCC is ordered, the minimum Gibbs free energy must be calculated in order to find the correct distribution of elements on the sites, and so the I-option must be used for this phase. See also the previous question on TiAl. 6.
For the body centered cubic structure (BCC) there is a disordered state in which atoms randomly occupy the sites, and there is an ordered state with preferential occupation of the sites. For the Fe-Al (and Fe-Si) system the transition of the disordered (Fe-rich) state into the ordered state at high Al- (and Si-) content has been modelled such that the Gibbs free energy of the disordered state (BCC_A2) is taken as the basis of the calculation and the ordering energy for B2_BCC is added as an extra but necessary contribution. Such a case is denoted by the by the full name B2_BCC!BCC_A2.
Related Questions
- Why is cementite a compound Fe3C in the compound database (SGSLbase) and a solution Fe-Cr-C in the solution database (SGSLSoln)?
- Where are the intermetallic compounds that are supposed to be part of the SGTE solution database?
- What is the purpose of the phase B2_BCC!BCC_A2 in the SGTE (SGSLsoln) solution database?
