Atomistic modelling of plasticity, cleavage and thermodynamics of metals and polymers
The proposal aims to ensure the computational resources for three separately externally funded projects dealing with atomistic modelling of tungsten, zirconium hydrides and polyethylene. Pär Olsson is the PI for all these projects: I) Project: “Atomistically informed multiscale modelling of intergranular fracture in tungsten”. Funded by the Swedish Research Council through grant 2016-04162. The project deals with classical atomistic and ab initio modelling of phosphorus inhabited grain boundaries in tungsten. We will study how impurities affect the grain boundary strength and ductility. This aims to generate atomistically informed cohesive zone models that can be used to modelling macroscopic failure in tungsten alloys by means of finite element modelling. The project includes generating an empirical interatomic MEAM potential for tungsten and phosphorus, which will be used to perform atomistic simulations of the impurity inhabited grain boundaries to extract the cohesive zone properties. The fitting database for the potential will be obtained from ab initio modelling. Tungsten alloys will be used for instance as plasma-facing materials in fusion reactors for which grain boundary failure poses as a serious problem. Hence, this project aims to provide a useful modelling tool that can be used to help ensure the integrity of the plasma-facing components in the future fusion reactors. II) Project: “Ab initio-based modelling of hydride stability in zirconium”. Funded by the Crafoord foundation through grant 2016-0740. Within the present project we aim to investigate the hydride stability in zirconium by means of combined ab initio and cluster expansion modeling. The primary objective is to elucidate the pressure and thermal conditions under which the gamma-hydride is formed. This is an elusive phase whose existence is widely debated in the scientific community. Within our research group we have recently found experimental evidence of its existence, and now we aim to use first principles modelling to map out the external conditions under which it is formed. Zirconium hydrides are notorious for being brittle and they are commonly formed in zirconium, which is widely used as fuel cladding in light and heavy water nuclear reactors. The long term ambition of this project is to understand hydride formation in nuclear fuel cladding materials, which will aid in making lifetime predictions for when in service and in dry storage. III) Project: “Modelling of continuum and damage Initiation and evolution in semi-crystalline polymer materials exerted to complex loading situations”. Funded by the Swedish Knowledge Foundation through grant 2015-0165. This multiscale project consists of an atomistic modelling part and a continuum modelling part. We apply for computational resources for the atomistic part of the project, in which we investigate the plasticity mechanisms in crystalline polyethylene (PE) by means of ab initio modelling and study the mechanical properties of semi-crystalline PE by means of empirical atomistic modelling. Through this project we aim to understand quantify the plasticity mechanisms in semi-crystalline polymers. Such knowledge will be translated into macroscopic continuum models that will be used to predict the failure of PE.