Metals and Alloys Resources - About

Mission and History

Peter Wallace, Chairman
The Metals and Alloys Subcommittee shall be responsible for (1) assuring that the metals and alloys subfile meets present and future needs of metallurgists and materials scientists, (2) developing and updating the metals and alloys subfile, (3) editing metals and alloys data and products to ensure a high standard of quality, and (4) extending the coverage and usefulness of the metals and alloys subfile, and (5) maintaining a web page on the ICDD site to communicate with members and other materials scientists.

Use of Alphabetical Formulae in the Metals and Alloys Subfile and products

Throughout M&A files and products, the elements within each formula are given in alphabetical order of the elemental symbols consistent with the procedure of Pearson1 and Villars and Calvert2, e.g., CFe3 and not Fe3C. In a practical sense, this means the empirical formulae are used.

1. Pearson, W. B., Handbook of Lattice Spacings and Structures of Metals, Pergamon Press, Oxford, 1967; Vol. 2, pp 1-4.
2. Villars, P.; Calvert, L. D. Pearson's Handbook of Crystallographic Data for Intermetallic Phases, American Society for Metals: Metals Park, OH, 1985; Vol. 1, pp 3-787.

Content and Scope of the Metals and Alloys Subfile

Periodic Table - A graphical definition of the scope and content of the Metals and Alloys subfile.


Metals and Alloys Selection Criteria - A description of the scope and content of the Metals and Alloys subfile.


This memorandum updates the metals and alloys phase-selection criteria in the reference memorandum and revisions 2 and 3 of the criteria.  Please send corrections, comments, or brickbats to the author at 687 West Soaring Hawk Place, Oro Valley, AZ 85737-6558 or

Metals, Alloys and Related Phases (M&A) Subfile Phase-Selection Criteria

The Metals and Alloys Subcommittee follows the criteria used by Pierre Villars and Larry Calvert in their updates of Pearson’s Handbook.  We have done so in order to ensure that the Powder Diffraction File’s M&A Subfile is consistent with and complementary to accepted metallurgical and materials references.


  • Editorial judgment is extremely important and must be used in deciding what is included in the subfile.  Use the rules below in conjunction with the exercise of that judgment.
  • In case of doubt about whether to include a phase, include it.

The phase-selection criteria are:

  • Only single-phase materials are included.  (Thus, common metallurgical mixtures such as pearlite are not included.)
  • All polymorphs of elemental metals are included.
  • All polymorphs of elemental arsenic, boron, carbon, hydrogen, nitrogen, oxygen, phosphorus, selenium, silicon, sulfur, and tellurium are included.
  • All polymorphs of the rare gases (Group VIII) are included.
  • All intermetallic compounds are included.
  • Oxides:
  • All binary metal oxides are included.
  • Ternary metal oxides are not included.  Exception:  If the phase (1) contains two metals due to solid-solution substitution and (2) is based on a binary oxide structure, it is included subject to the following limitation.  If the substituting-cation concentration exceeds10 percent of the total occupancy of the binary oxide site, the phase is not included.
  • Quaternary and higher oxides are not included.
  • All metal arsenides, carbides, hydrides, phosphides, selenides, sulfides, and tellurides are included, regardless of the number of metals involved.
  • All binary compounds of boron or silicon with arsenic, carbon, nitrogen, oxygen, phosphorus, selenium, sulfur, and tellurium are included.
  • Compounds between arsenic, phosphorus, selenium, sulfur, and tellurium are permitted to the extent that Villars has included them.
  • No halide (Group VII) compounds are included.
  • No inert-gas (Group VIII) compounds other than binary oxides are included.
  • No hydrous materials (e.g., hydrates and hydroxides) are included.

Some examples of what is included in the subfile and what is not are on the next two pages.

Examples of Phases That Are Included in the Metals and Alloys Subfile

  • [single-phase] Alloys
  • Arsenides
  • Azides ... Hg(N3)2, CsSr(N3)2
  • Boranes ... B12H16, B16H20
  • Borides
  • Carbides
  • [pure, solid] Group VIIIA elements (rare gases)
  • Hydrides, deuterides, and tritides
  • Ice ... H2O [or D2O or OT2]
  • Intermetallic compounds
  • [pure] Metals
  • Nitrides
  • [binary] Oxides (including those of the Group VIII elements)
  • Peroxides ... H2O2 , D2O2, and O2T2
  • Phosphides
  • Selenides
  • Silicides
  • Sulfides
  • Tellurides

  • Ba(BH4)2, Ca(BH4)2, U(BH4)4
  • CxOy,
  • H2S
  • KHS, NaHS
  • NH3 [solid-ammonia polymorphs]
  • NxOy
  • NxSy
  • Pu(C, O)  (if the ClNa prototype structure is maintained)
  • PxOy
  • PxSy
  • Rb2HP6N11
  • SxOy

  • Examples of Phases That Are Not Included in the Metals and Alloys Subfile

  • Amides ... K(NH2)
  • Aminoimides ... N4H4
  • Ammonia-containing materials ... Ir (NH3)5
  • Ammonium-containing materials ... NH4CuWS4
  • Borazine ... B3N3H6
  • Bromides
  • Carboborane … B4C2H8
  • Carbonates
  • Carbonyls ... N3(NB9H11)(CO)
  • Chlorides
  • Cyanamides ... Li2CN2 , Zn2CN2
  • Cyanides ... Rb(CN)
  • Fluorides
  • [compounds of] Group VIIIA elements other than binary oxides
  • Hydrates
  • Hydrazines ... ZnSe:N2H4
  • Hydroxides
  • Imides ... BaNH , MgNH , Ca2NH
  • Iodides
  • Nitrates
  • Nitrites
  • [ternary or higher] Oxides  (See exception on page 2, no. 6.)
  • Silicates
  • Sulfates
  • Sulfites
  • Thiocarbamates ... PbCS3
  • Thiocyanates ... RbBi(SCN)4

  • H2CS3
  • Nb(NO)  [when no comma is between N and O]