Title:	Accelerated ab initio molecular dynamics: plastic deformation in ceramics
DNr:	LiU-2018-22
Project Type:	LiU Compute
Principal Investigator:	Davide Sangiovanni <davide.sangiovanni@liu.se>
Affiliation:	Linköpings universitet
Duration:	2018-11-01 – 2019-11-01
Classification:	10304
Keywords:

Abstract

Transition metal nitrides and carbides (TMN and TMC) are extremely hard but also brittle. Experiments show that these ceramic materials undergo brittle-to-ductile transitions at temperatures close to 1000 K. Combining experiments and density-functional theory (DFT) calculations, we have demonstrated that alloying TiN, TiAlN, and VN with MoN and WN increases both hardness and ductility/plasticity even at room temperature. Nevertheless, the atomistic mechanisms controlling plastic deformation in nitrides and carbides are unknown. Ab initio molecular dynamics (AIMD) is the most reliable computational tool available to determine the mobility of dislocations and reveal plastic deformation dynamics at finite temperatures. Due to the high computational demand of AIMD, we use acceleration methods that we have developed, which allows us to reduce simulation times up to 3-4 orders of magnitude. During the past ~12 months we have published 12 papers where SNIC resources have been acknowledged. Financial support from Knut and Alice Wallenberg Foundation (No. 2011.0094), the Swedish Research Council (VR) (Grants 2008-6572 and 2014-5790 and 2013-4018), and the Olle Engkvist Foundation. 1. Edström, Sangiovanni, et al. Effects of incident N atom kinetic energy on TiN/TiN(001) film growth dynamics: A molecular dynamics investigation Journal of Applied Physics 121, 025302 (2017) 2. Mikula, Sangiovanni, et al. Thermally induced age hardening in tough Ta-Al-N coatings via spinodal decomposition Journal of Applied Physics 121, 155304 (2017) 3. Mikula, Truchlý, Sangiovanni, et al. Experimental and computational studies on toughness enhancement in Ti-Al-Ta-N quaternaries Journal of Vacuum Science & Technology A 35, 060602 (2017) 4. Gambino, Sangiovanni, et al. Nonequilibrium ab initio molecular dynamics determination of Ti monovacancy migration rates in B1 TiN Physical Review B 96, 104306 (2017) 5. Zheng, Mei, Tuteja, Sangiovanni, et al. Phonon and electron contributions to the thermal conductivity of VNx epitaxial layers Physical Review Materials 1, 065002 (2017) 6. Edström, Sangiovanni, et al. Elastic properties and plastic deformation of TiC- and VC-based pseudobinary alloys Acta Materialia 144, 376 (2018) 7. Sangiovanni, Mei, Edström, et al. Effects of surface vibrations on interlayer mass transport: Ab initio molecular dynamics investigation of Ti adatom descent pathways and rates from TiN/TiN(001) islands Physical Review B 97, 035406 (2018) 8. Sangiovanni Inherent toughness and fracture mechanisms of refractory transition-metal nitrides via density-functional molecular dynamics Acta Materialia 151, 11 (2018) 9. Sangiovanni Copper adatom, admolecule transport, and island nucleation on TiN(001) via ab initio molecular dynamics Applied Surface Science 450, 180 (2018) 10. Sangiovanni, Gueorguiev, Kakanakova-Georgieva Ab initio molecular dynamics of atomic-scale surface reactions: insights into metal-organic chemical vapor deposition of AlN on graphene Physical Chemistry Chemical Physics 20, 17751 (2018) 11. Gambino, Alling Lattice relaxations in disordered Fe-based materials in the paramagnetic state from first principles Physical Review B 98, 064105 (2018) 12. Ekholm, Gambino, et al. Assessing the SCAN functional for itinerant electron ferromagnets Physical Review B 98, 094413 (2018)