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ERIC Number: EJ936760
Record Type: Journal
Publication Date: 2011-May
Pages: 5
Abstractor: As Provided
Reference Count: 50
ISSN: ISSN-0021-9584
Thermodynamics of Condensed Phases: Formula Unit Volume, "V[subscript m]", and the Determination of the Number of Formula Units, "Z", in a Crystallographic Unit Cell
Glasser, Leslie
Journal of Chemical Education, v88 n5 p581-585 May 2011
Formula unit (or molecular) volume, "V[subscript m]", is related to many thermodynamic and physical properties of materials, so that knowledge of "V[subscript m]" is useful in prediction of such properties for known and even hypothetical materials. The symbol "Z" represents the number of formula units in a crystallographic unit cell; "Z" thus permits calculation of "V[subscript m]" from the unit-cell volume. Unfortunately, "Z" is sometimes omitted from published crystal constants (for obscure reasons). We discuss methods for evaluation of "Z" and "V[subscript m]", and some of the complications in the assessment of "Z". We show how entropy, lattice energy, and bulk isothermal compressibility (a thermoelastic property) are calculated using thermodynamic correlations, with the chalcopyrite CuAlS[subscript 2] as an example. (Contains 5 figures and 1 note.)
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A