Teacher:In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Teacher: Now, understand the problem? Solve this instance: What compound  structure does not refer to a ratio?, Context: An alloy is a mixture of metals or a mixture of a metal and another element. Alloys are defined by metallic bonding character. An alloy may be a solid solution of metal elements (a single phase) or a mixture of metallic phases (two or more solutions). Intermetallic compounds are alloys with a defined stoichiometry and crystal structure. Zintl phases are also sometimes considered alloys depending on bond types (see also: Van Arkel-Ketelaar triangle for information on classifying bonding in binary compounds).
Student:
crystal structure