Agradecimentos: This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 with PROSUC/CAPES scholarships (L. M. L., D. M. and G. L. R), by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) - grants 304831/2014-0 and 305253/2018-2 (CAP), 304675/2015-6 and 305528/2018-1 (JEZ), 302370/2015-3 (FA) and 308567/2018-8 (CAF), Programa de Apoio a Núcleos de Excelência (PRONEX), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS) - Project 2019/18460-4 - FAPESP-FAPERGS. This research was also made possible thanks to computational resources provided by the Centro de de Computação Científica (NCC/GridUNESP), Universidade Estadual de São Paulo (UNESP), Núcleo Avançado de Computação de Alto Desempenho (NACAD) da COPPE, Universidade Federal do Rio de Janeiro (UFRJ), and Centro Nacional de Supercomputação, Universidade Federal do Rio Grande do Sul (CESUP/UFRGS) Ver menos

Abstract: Friction behavior at the nanoscale may be split into different contributions, including phononic dissipation. Despite the isotopic effect in the phononic component being previously explored, experimental and theoretical approaches determined contradictory conclusions. Here, a desorption-based model is proposed, and it is found to be consistent with previously published experimental data on hydrogenated and/or deuterated amorphous carbon films. Moreover, molecular dynamics simulations showed that a surface coverage difference as low as 5% might promote an effect on friction even greater than that observed experimentally. This happens when reactive defects are created after desorption (prompting carbon dangling bonds), reinforcing the assumption that minor surface differences may be sufficient for the effects observed, meeting both experimental and theoretical approaches in the same overall trend. Therefore, the phononic dissipation occurs, but the isotopic effect may be indirect, where the desorption rate of hydrogen and deuterium plays a role by exposing carbon dangling bonds, changing the interface of interaction and the nanoscale friction ultimately Ver menos