The Stokes-Einstein-Debye relation in ortho-terphenyl liquid

TL;DR

This study uses molecular dynamics simulations to evaluate the validity of the original Stokes-Einstein-Debye relation in supercooled ortho-terphenyl, finding it holds true while variants do not, due to assumptions and molecular interactions.

Contribution

The paper provides evidence that the original SED relation is valid for OTP, clarifying misconceptions caused by variants and highlighting factors affecting their validity.

Findings

Original SED relation is valid for OTP

Variants of the SED relation are invalid in this context

Heterogeneous dynamics and molecular interactions cause discrepancies

Abstract

The Stokes-Einstein-Debye (SED) relation is proposed to be breakdown in supercooled liquids by many studies. However, the conclusions are usually drawn by testing some variants of the SED relation rather than its original form. In this work, the rationality of the SED relation and its variants is examined by performing molecular dynamics simulations with the Lewis-Wahnstrom model of ortho-terphenyl (OTP). The results indicate the original SED relation is valid for OTP but the three variants are all breakdown. The inconsistency between SED relation and its variants is attributed to the adopted assumptions and approximations, heterogeneous dynamics and the interactions among molecules. Therefore, care should be taken when employing its variants to judge the validity of the SED relation in supercooled liquids.