title: Molecular mechanics of elastic and bendable caffeine co-crystals.
abstract: Complementing recent experimental results, here we report a computational study of remarkably flexible, elastically bendable caffeine cocrystals (cocrystal solvate 1), formed from caffeine (CAF), 4-chloro-3-nitrobenzoic acid (CNB), and methanol, and compare with its unsolvated brittle form, 1 (dry). We show that 1 is able to maintain stable cocrystal structures at temperatures between 100 K and 400 K. The tensile and compressive Young's modulus of 1 are close to ~10 GPa. The ultimate strength is more than 600 MPa in tensile and 400 MPa in compressive at temperature of 100 K. The simulation results of the structural and mechanical properties of 1 are in good agreement with our previous experimental work. Notably, before the ultimate tensile stress, the stress-to-strain curves of 1 show linear behavior, but 1 (dry) show nonlinear behavior. This study might explain the remarkable elasticity of 1 and is relevant to the design of high-performance organic materials with excellent self-healing or efficient stress dissipating properties.
authors.affiliation: Laboratory for Atomistic and Molecular Mechanics (LAMM), Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave. Room 1-235A&B, Cambridge, Massachusetts 02139, USA. mbuehler@MIT.EDU.
authors.forename: Chun-Teh
authors.initials: CT
authors.lastname: Chen
authors.forename: Soumyajit
authors.initials: S
authors.lastname: Ghosh
authors.forename: C Malla
authors.initials: CM
authors.lastname: Reddy
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Buehler
mesh_terms: D002110:Caffeine / Q000737:chemistry*; D002723:Chlorobenzoates / Q000737:chemistry*; D019245:Compressive Strength; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D055119:Elastic Modulus; D006244:Hardness; D008422:Materials Testing; D000432:Methanol / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D002723:Chlorobenzoates; D012997:Solvents; C040769:4-chloro-3-nitrobenzoic acid; D002110:Caffeine; D000432:Methanol