NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
An Equation of State for the Thermodynamic Properties of Helium
Published
Author(s)
Diego Ortiz Vega, Kenneth Hall, James Holste, Allan H. Harvey, Eric W. Lemmon
Abstract
This report documents the equation of state for fluid helium implemented in Version 10 of NIST's REFPROP Standard Reference Database. The equation of state is expressed as the molar Helmholtz energy as a function of temperature and density, and is valid for the normal fluid (helium I) up to 1500 K and 2000 MPa. Limited comparisons with experimental data and with virial coefficients calculated by ab initio methods are provided.
Ortiz Vega, D.
, Hall, K.
, Holste, J.
, Harvey, A.
and Lemmon, E.
(2023),
An Equation of State for the Thermodynamic Properties of Helium, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.IR.8474, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956186
(Accessed October 9, 2025)