title: First-Principles Calculation of the Third Virial Coefficient of Helium.
abstract: Knowledge of the pair and three-body potential-energy surfaces of helium is now sufficient to allow calculation of the third density virial coefficient, C(T), with significantly smaller uncertainty than that of existing experimental data. In this work, we employ the best available pair and three-body potentials for helium and calculate C(T) with path-integral Monte Carlo (PIMC) calculations supplemented by semiclassical calculations. The values of C(T) presented extend from 24.5561 K to 10 000 K. In the important metrological range of temperatures near 273.16 K, our uncertainties are smaller than the best experimental results by approximately an order of magnitude, and the reduction in uncertainty at other temperatures is at least as great. For convenience in calculation of C(T) and its derivatives, a simple correlating equation is presented.
authors: CNISM and Dipartimento di Fisica, Università di Trento, via Sommarive 14, 38100 Povo (TN), Italy.
authors: Giovanni
authors: G
authors: Garberoglio
authors: Thermophysical Properties Division, National Institute of Standards and Technology, 325 Broadway, Boulder CO 80305, USA.
authors: Allan H
authors: AH
authors: Harvey
keywords: calibration; density; helium; metrology; path integral; thermodynamic properties; virial coefficients