Fast Track Communication Tensile strength of carbyne chains in varied chemical environments and structural lengths Reza Mirzaeifar, Zhao Qin and Markus J Buehler Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA, USA E-mail: mbuehler@MIT.EDU Received 5 July 2014 Accepted for publication 22 July 2014 Published 22 August 2014 Abstract Carbyne and carbyne-based low-dimensional structures are promising for several applications including ultra-compact circuits and purification devices. Designing any applied carbyne-based structure requires a fundamental understanding of the mechanical strength of carbyne chains with different lengths at different temperatures and operating chemical environment. Here we use molecular dynamics simulations to investigate the strength of carbyne chains with different lengths at different temperatures. A theoretical framework based on statistical mechanics and molecular dynamics results is presented, proving a fast and insightful method for predicting the rupture force and its physical mechanism. The effect of water molecules’ interaction is also studied on the mechanical properties and it is shown that both the tensile strength and rupture strain are improved by the water interaction. The results of this work can be used for designing and analyzing the robustness and reliability of various carbyne-based materials and applied devices for varies working conditions. Keywords: carbyne, molecular mechanics, rupture, elasticity, Bell theory, size effect, chemical environment (Some figures may appear in colour only in the online journal) 1. Introduction Carbyne is a one-dimensional carbon allotrope composed of sp-hybridized carbon atoms, which in theory consists of either double-bonded structure (polycumulene) or alternating single- triple bonds (polyyne) [1–3]. Several chemical methods were proposed for synthesizing stable finite-length carbon chains [4–7]. The intense interest in studying the structure and mechanics of carbyne [8–13], besides experimental efforts for fabricating carbyne chains with different lengths is because of its novel electron transport mechanism, possible applications as graphene interconnectors [14], its prospect of being used as a component in atomistic scale circuits [9, 10], and also other possible technological breakthroughs. The mechanical properties of carbyne have been exten- sively investigated using various methods including mole- cular dynamics (MD) simulations, and first-principles calculations [8–10]. However, it is largely unknown how the mechanical properties of this structure are affected by the environmental factors in applications (e.g., filtration and water purification devices), particularly the effect of chain length, temperature and chemical environment on the fracture force of carbyne chains. Recent achievements in studying and synthesizing complex molecular mechanisms based on car- byne chains [15–18] and potential unique applications for these new structures motivated us to investigate those effects. For example, one major application by understanding the mechanics of carbyne is accessing the mechanical strength of graphyne in various working conditions [15, 19]. Graphyne is Nanotechnology Nanotechnology 25 (2014) 371001 (7pp) doi:10.1088/0957-4484/25/37/371001 0957-4484/14/371001+07$33.00 © 2014 IOP Publishing Ltd Printed in the UK 1