Editor's Pick on The Journal of Chemical Physics

20 December 2021

A recent paper co-authored by an ECT* researcher, Giovanni Garberoglio, has been selected as Editor’s Pick in The Journal of Chemical Physics.
This work, in collaboration with NIST and the University of Warsaw, paves the way for an accurate first-principles calculation of the third dielectric virial coefficient of the helium gas. It extends to dielectric quantities a trend that has been influencing primary metrology in the past 20 years: some thermophysical properties of the helium gas can be computed with an uncertainty smaller than that of the best experimental measurements. This is achieved by developing a theoretical and computational pipeline that begins from the complete numerical solution of the electronic structure of helium atoms (including relativistic effects) from which few-body potentials and polarizabilities, both with well-defined uncertainties, can be derived. These quantities are in turn used to compute virial coefficients solving the exact formulae from quantum statistical mechanics within a path-integral formalism.
At the end of this process, virial coefficients and their propagated uncertainties are computed directly from the fundamental equations of physics with no uncontrolled approximation.

Presently, the imperfect knowledge of the third dielectric virial coefficient is the among the largest sources of experimental uncertainty in dielectric-constant gas thermometry (DCGT), one of the most accurate techniques to measure temperature and pressure which is been put forward as a primary standard after the 2019 redefinition of the SI base units. It is expected that a completely theoretical calculation of the third dielectric virial coefficient with fully characterized uncertainty – currently in progress – will increase by a factor of two the already impressive accuracy (of the order of 1 part per million) of DCGT.
ECT* is participating with several theoretical and experimental groups to two European projects aimed at pushing forward novel techniques for primary metrology of temperature and pressure.

Read the paper HERE