SPECIAL ISSUE CONTRIBUTION A novel multiscale approach to brittle fracture of nano/micro‐sized components Michal Kotoul 1,2 | Petr Skalka 1,2 | Tomáš Profant 1,2 | Petr Řehák 1,2 | Petr Šesták 1 | Miroslav Černý 1,2 | Jaroslav Pokluda 1,2,3 1 Central European Institute of Technology, Brno University of Technology, CEITEC BUT, Purkyňova 123, Brno 612 00, Czech Republic 2 Faculty of Mechanical Engineering, Brno University of Technology, Technická 2896/2, Brno 616 69, Czech Republic 3 Faculty of Special Technology, Alexander Dubcek University of Trencin, Pri parku 19, Trenčín 911 06, Slovak Republic Correspondence Michal Kotoul, Advanced Metallic Materials and Metal Based Composites, CEITEC BUT, Purkyňova 123, Brno 612 00, Czech Republic. Email: kotoul@fme.vutbr.cz Funding information Grantová Agentura České Republiky, Grant/Award Number: 17‐18566S; Minis- try of Education, Youths and Sports of the Czech Republic, Grant/Award Number: LM2015070 Abstract Principles and advantages of a new concept based on the ab initio aided strain gradient elasticity theory are shown in comparison with the classical Barenblatt cohesive model. The method is applied to the theoretical prediction of the critical energy release rate and the crack tip opening displacement at the crack instability in nanopanels made of germanium and molybdenum crystals. The necessary length scale parameter l 1 is determined for germanium and molybdenum by the best gradient elasticity fits of ab initio computed screw dis- location displacements and phonon dispersions. Values of ab initio computed critical energy release rates and crack opening profiles revealed that the length l 1 is related to inflexion points of profiles. A novel ab initio method in combi- nation with continuum mechanics was successfully tested to replace molecular statics dependent of availability of interatomic potentials. The asymptotic strain gradient elasticity solution for displacement components near the crack tip in materials with cubic lattice was also derived. KEYWORDS DFT, FEM, fracture nanomechanics, size‐dependent phenomena, strain gradient elasticity 1 | INTRODUCTION The fracture mechanics based on the classical elasticity theory (CET) describes the fracture phenomenon and postulates the critical conditions at which the crack becomes unstable. It adopts and extensively develops the Irwin's concept 1 of the stress intensity factor (SIF) for various kinds of the fracture problems. All these stud- ies of the fracture mechanics do not exceed the specimen size limits from meters to micrometers and keep the restriction given by the basic hypothesis of the linear fracture mechanics, which says that the size of the region, where the stress components are controlled by SIF (K‐ dominant region), must be much higher than the fracture process zone incorporating inelastic deformations near the crack tip. Although the success of this continuum concept in the theoretical and practical level is indisput- able, it is not able to respond the question regarding the sufficiency of SIF to predict the fracture of cracked nanocomponents typically used in microelectronic devices. The atomistic calculations have to be included into the considerations if the continuum mechanics is to Received: 25 October 2019 Accepted: 26 November 2019 DOI: 10.1111/ffe.13179 Fatigue Fract Eng Mater Struct. 2019;1–16. © 2019 Wiley Publishing Ltd. wileyonlinelibrary.com/journal/ffe 1