PHASEFIELD

Approximations to dynamic density functional theory - phase field simulations on atomic scales

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 Obiettivo del progetto (Objective)

'A recent innovation in materials modeling has been the phase field crystal model. Instead of a phenomenological phase field variable the quantity of interest is the atomic number density. This formulation has made it possible to incorporate the kinetics of phase transformations with properties of solids that arise due to their periodic structure. This includes elastic strain, topological defects, vacancy diffusion and polycrystalline grain boundary interactions. The appealing feature of the phase field crystal model is its connection with classical density functional theory, which allows material specific simulations on diffusive time scales, orders of magnitude larger than classical molecular dynamics.

Our mission is to foster international cooperation in phase field crystal modeling and serve as a platform for addressing global challenges in materials science by using the phase field crystal approach. Applications of interest are self-assembly of quantum dots in thin film growth and fluid-structure interactions in microfluidics.

We involve participants from diverse sectors, regions and science and engineering disciplines which have already proven to be able to work together efficiently.'

Introduzione (Teaser)

The key to predicting and therefore controlling properties of materials is knowledge of their microstructure. An EU-funded project is developing models able to describe microstructures of realistic complexity at time scales of practical interest.

Descrizione progetto (Article)

The phase-field approach has become the method of choice for modelling complicated microstructures during phase transformations (namely changes in the pattern of atoms) elastic and plastic deformation. It can characterise microstructures and their evolution in time and space under realistic conditions with the use of conserved and non-conserved variables.

However, adoption of the phase field approach in practical applications has been slow because current phase field microstructure modelling is qualitative in nature.

The aim of the 'Approximations to dynamic density functional theory - Phase field simulations on atomic scales' (PHASEFIELD) is to increase simulations length and time scales for quantitative modelling self-assembly of quantum dots and molecular interactions in microfluidics devices.

Several milestones have been reached in this direction. Using the phase field approach, the microstructure of a crystalline material is modelled by high-order partial differential equations that are valid at atomic scales. They cannot generally be solved analytically, but the PHASEFIELD researchers have been developing tools to solve them numerically. The continuous equations were replaced with their discrete counterparts and the time step was adapted to obtain meaningful solutions.

Furthermore, the relationship between the phase field modelling and the classical atomic density functional theory is examined.

Specifically, a connection is made between the free energy, capturing the thermodynamics of crystals and using atomic number density.

The purpose of linking the formalism of the classical theory with the newest extension of the phase field modelling is to exploit the connection to develop multiscale models.

Although significant progress has been made, many challenges still remain. Exactly how capable microstructure modelling is at revealing how the materials must be handled to define microstructure needs to be evaluated. This is one of the key elements in materials quality control defining the final functionality of materials. For example, the crystal structure and impurity content of silicon determines its performance in electronics.

In Europe, technological advance has always been linked to the ability to engineer new material and exploit their properties. Modelling at the atomic scale pursued within the PHASEFIELD project is likely to have a revolutionary impact on the way materials are designed and manufactured in the future.