Phase Names For searches phase names following rules

Phase Names ? ? ? • • For searches phase names following rules are imperative Reinterpretation of reported results may result in erroneous entries Al-Mg

Challenge of Phase Names • What is γ? § Austenitic phase in Fe-alloys § Ni-phase in superalloys § Ti. Al phase in Ti-Al based alloys § Mg 17 Al 12 phase in light weight alloys • § Cu 5 Zn 8 phase in brass. How to name phases that form extensive homogeneity ranges in higher component system because of the same crystal structure but have different names in the subsystems?

• Phase Names § No general accepted method § Recommend proposal by Schmid-Fetzer et al. , CALPHAD 2007 • Phases that form a continuous solution ► Strukturbericht designation + lattice e. g. A 1_FCC, DO/19_HCP. • Phases that form no continuous solutions ► • • ► Strukturbericht designation with phase structure information (e. g. B 1_Halide and B 1_Carbide) But B 1_Carbide, B 1_Nitride, B 1_Carbonitride, …? Crystal Structures: 3 -D patterns of atomic arrangements Crystal Structures: § Many different crystal structures § Many compounds with different chemistries can have the same crystal structure § Consistent identification of unique crystal structure is needed: Space group + Wyckoff sequence Suggestion: Use a format based on the In. Ch. I (International Suggestion: Chemical Identifier, IUPAC) § Non-proprietary identifier for chemical substances enabling easier linking of diverse data compilations

In. Ch. I • • International Chemical Identifier Initial release in April 2005, IUPAC / In. Ch. I Trust String of characters uniquely identifying a chemical compound Layered structure allows various levels of details § Only main layer is required: atoms and bonds § Other layers with specific information optional • • Separated by “/” • Begin with characteristic prefix letter Covers mainly organic molecules Ethanol: In. Ch. I=1 S/C 2 H 6 O/c 1 -2 -3/h 3 H, 2 H 2, 1 H In. Ch. IKey = hashed counterpart

Some Phase Name Examples Phase name Strukturbericht designation Prototype Chemical formulae Comment A 1_Fcc A 1 Cu Al, Ni, Cu, … A 2_Bcc A 2 W V, Cr, Mo, … A 3_Hcp A 3 Mg Be, Mg, Ti, … B 1_Fcc B 1 Na. Cl Ti. C, Nb. C, Ta. C, … B 1_Oxide B 1 Na. Cl Ca. O, Fe. O, Ti. O… B 2_Bcc B 2 Cs. Cl Al. Ni, Al. Fe, Fe. Ti, … Ordered bcc B 2_Halide B 2 Cs. Cl, Tl. Br, KI “Independent” B 2 L 10_FCC L 10 Au. Cu Al. Ti, Mn. Ni, Fe. Pt, … Ordered fcc D 019_Hcp D 019 Ni 3 Sn Al. Ti 3, Co 3 W, Co. Zr 3, … Ordered hcp C 14_Laves C 14 Mg. Zn 2 Cr 2 Ti, Hf. Mn 2, Ni 2 U, … C 15_Laves C 15 Mg. Cu 2 Cr 2 Ti, Co 2 Ti, Ni 2 Y, … Mu D 85 Fe 7 W 6 Co 7 Mo 6, Fe 7 Nb 6, Ni 7 Ta 6, … Sigma D 8 b Cr. Fe Al. Nb 2, Cr 3 Mn, Cr 2 Re 3, … Me 3 Si … PTi 3 As. Nb 3, Ge. Zr 3, Si. Ti 3, … Limited to combination of transition metal with metalloid Al 3 Fe … Al 3 Fe, Al 13 Ru 4 Only two compounds known with this structure Al 2 Fe … Al 2 Fe No other chemistry known Al 3 Co … … Al 3 Co Structure unknown

A 1_Fcc or Fcc_A 1? • • A 1_Fcc, L 12_Fcc, C 14_Laves etc. convenient for auto completion Inconsistencies in Calphad tradition: Fcc_A 1 but C 14_Laves. Hierarchically top-down from left to right gives: Fcc_A 1, Fcc_L 12 and Laves_C 14, Laves_C 15 More considerations: § A 1 in conjunction with fcc is redundant § L 12_fcc identifies a phase that is described as an ordered version of fcc § Laves in combination with C 14, C 15 and C 36 is also redundant as all three phases are Laves phases. § Need to describe variants of the different phases: B 1_Halide, B 1_Carbide, C 14_Cr 2 Zr, C 15_Cr 2 Zr, etc. § This could lead to B 1_Halide_Na. Cl but this again is redundant

Suggestion for Identifier Structure Constructing an identifier using the concept of the In. Ch. I • Could contain records formula, a general tag for the aggregate state, SOL, LIQ or GAS • Tags: prototype (PT), Pearson symbol (PS), Strukturbericht designation (SD), space group (SG, using the number), Wyckoff sequence (WS), site occupation (SO) of the Wyckoff positions • Incorporate phase name – which layer? pure fcc Fe Fe/SOL/PT: Cu/PS: c. F 4/SD: A 1/SG: 225/WS: a/SO: a: Fe 1 interstitial solution of N in fcc Fe Fe. N 0. 0897/SOL/PT: Fe. Nx/PS: c. F 4/SD: A 1/SG: 225/WS: ab /SO: a: Fe 1: b: N 0. 0897 off-stoichiometric compound Ti. C 0. 957/SOL/PT: Na. Cl/PS: c. F 8/SD: B 1/SG: 225/WS: ab /SO: a: Ti 1: b: C 0. 947 prototype Ni. As/SOL/PT: Ni. As/PS: h. P 4/SD: B 81/SG: 194/WS: ac /SO: a: Ni 1: c: As 1 prototype Ni 2 In/SOL/PT: Ni 2 In/PS: h. P 6/SD: B 82/SG: 194/WS: acd /SO: a: Ni 1: c: In 1: d: Ni 1 phase with partially filled sites Au 0. 62 Pd 0. 74 Sn/SOL/PT: Ni. As/PS: h. P 4/SD: B 81/SG: 194 /WS: acd/SO: a: Au 0. 62, Pd 0. 38: c: Sn: d: Pd 0. 36 regular liquid Ag. Au/LIQ/LT: regular/SP: Ag, Au type of liquid (LT) short range ordered liquid Mn. O/LIQ/LT: ionic/SP: Mn+2, Mn+3: O-2, Va-q CALPHAD slang? As gas As: /GAS/SP: As, As 2, As 4 special species (SP) site b, in contrast to the previous examples, is almost filled additional site (d) is filled compared to Ni. As