1 Scientific RepoRts | 7: 3242 | DOI:10.1038/s41598-017-03046-8 www.nature.com/scientificreports on the phonon dissipation contribution to nanoscale friction by direct contact s. R. sales de Mello 1 , M. e. H. Maia da Costa 2 , C. M. Menezes 1 , C. D. Boeira 1 , F. L. Freire Jr 2 , F. Alvarez 3 & C. A. Figueroa 1 the friction phenomenon is a ubiquitous manifestation of nature. Models considering phononic, electronic, magnetic, and electrostatic interactions are invoked to explain the fundamental forces involved in the friction phenomenon. In order to establish the incidence of the phonon prompting at the nanoscale friction by direct contact, we study a diamond spherical dome sliding on carbon thin ilms containing diferent amount of deuterium and hydrogen. The friction coeicient decreases by substituting hydrogen by deuterium atoms. this result is consistent with an energy dissipation vibration local mechanism from a disordered distribution of bond terminators. he understanding of the physical causes and how controlling friction properties is a cutting edge challenge in order to save energy, diminishing wear, increasing the lifetime and sustainability of mechanical devices, and improving performance 1, 2 . From Leonardo da Vinci’s and Guillaume Amontons’s ancient experiments up to the present time, the friction efects continue demanding enforces to explain the observed phenomenon 3, 4 . Indeed, the non-conservative forces acting in the physical interaction between two surfaces in relative motion is not explained by a unique and fundamental physical mechanism. his is in part due to the complexity of the dissipative forces involved in the phenomenon, strongly depending on the length scales of the sliding parts 5–7 . Furthermore, one of the most challenging ields in tribology concerns with the connection between the engineer- ing (macro) phenomenological models and physical fundamental (atomic and nanoscale) laws. By the lack of better tools, molecular dynamics calculations are applied to inspect the macroscopic phenom- enological three-term kinetic friction model (or part of it) to phenomena occurring at the nanoscale size 5, 6 . his model assumes the combination of three efects, namely, the adhesion force in the presence of a lubricant at zero normal load (Derjaguin ofset), the coeicient of friction (da Vinci-Amontons-Coulomb law) and the efective shear stress (Bowden-Tabor law) 6 . Although this approach brings valuable information for practical applications, several basic answers remain pending as, for example, the physical nature of the Derjaguin ofset, the physical understanding of the origin of the friction coeicient, and the inluence of the shear stress on the phenomenom. herefore, an attempt to improve the understanding of the three-term kinetic friction model by using fundamental physical properties of the matter could help to unify several mechanisms prompting the friction at the nanoscale size that seem disconnected at the present. From a statistical thermodynamically point of view, the friction phenomenon is one of the physical manifes- tations of the luctuation-dissipation theorem (FDT) 8 . his important theorem explains the transition from the microscopic reversibility physical process to a macro irreversibly phenomena involving energy dissipation, i.e., entropy increasing 9 . Recently, the FDT was invoked to explore the electrostatic coupling between induced dipoles of two atoms 10 . Moreover, diferent mechanisms dealing with phonons, electronic band transitions, magnetic and electrostatic interactions were proposed to explain nanotribological efects. Whatever the origin of the fric- tion fundamental mechanism involved in the phenomenon, any study must start taking into account the energy exchange (luctuation) and its subsequent dissipation between the sliding surfaces. Several works have explored the physical nature of energy exchange, coupling interaction, and dissipation mechanisms afecting the phenomenological friction coeicient and shear stress between sliding surfaces 8 . For instance, the superconducting transition drops abruptly the friction force of niobium thin ilms and solid nitro- gen along a lead surface 11, 12 . he abrupt modiication of the friction coeicient is attributed to fundamental 1 Centro de Ciências Exatas e da Tecnologia, Universidade de Caxias do Sul, Caxias do Sul-RS, 95070-560, Brazil. 2 Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro - RJ, 22453-900, Brazil. 3 Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, Campinas-SP, 13081-970, Brazil. Correspondence and requests for materials should be addressed to C.A.F. (email: caiguer@ucs.br) Received: 26 January 2017 Accepted: 19 April 2017 Published: xx xx xxxx opeN