Research Topic

Method development projects

Method Development Projects

<div style="text-align: justify;">Complex simulation protocols combine distinctly different computer codes and have to run on heterogeneous computer architectures. To enable these complex simulation protocols, the CM department has developed pyiron.</div>

pyiron - an integrated development environment (IDE) for computational materials science

Complex simulation protocols combine distinctly different computer codes and have to run on heterogeneous computer architectures. To enable these complex simulation protocols, the CM department has developed pyiron.
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<p>Combining concepts of semiconductor physics and corrosion science, we develop a novel approach that allows us to perform ab initio calculations under controlled potentiostat conditions for electrochemical systems. The proposed approach can be straightforwardly applied in standard density functional theory codes.</p>

Ab initio potentiostat

Combining concepts of semiconductor physics and corrosion science, we develop a novel approach that allows us to perform ab initio calculations under controlled potentiostat conditions for electrochemical systems. The proposed approach can be straightforwardly applied in standard density functional theory codes.

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The balance between different contributions to the high-temperature heat capacity of materials can hardly be assessed experimentally. In this study, we develop computationally highly efficient ab initio methods which allow us to gain insight into the relevant physical mechanisms. Some of the results have lead to breakdown of the common interpretation of temperature dependencies.

Anharmonicity and vacancies in Al

The balance between different contributions to the high-temperature heat capacity of materials can hardly be assessed experimentally. In this study, we develop computationally highly efficient ab initio methods which allow us to gain insight into the relevant physical mechanisms. Some of the results have lead to breakdown of the common interpretation of temperature dependencies. [more]
It is very challenging to simulate within DFT extreme electric fields (a few 10<sup>10</sup> V/m) at a surface, e.g. for studying field evaporation, the key mechanism in atom probe tomography (APT). We have developed a straight-forward scheme to incorporate an ideal plate counter-electrode in a nominally charged repeated-slab calculation by means of a generalized dipole correction of the standard electrostatic potential obtained from fully periodic FFT.

Generalized dipole correction for charged slabs

It is very challenging to simulate within DFT extreme electric fields (a few 1010 V/m) at a surface, e.g. for studying field evaporation, the key mechanism in atom probe tomography (APT). We have developed a straight-forward scheme to incorporate an ideal plate counter-electrode in a nominally charged repeated-slab calculation by means of a generalized dipole correction of the standard electrostatic potential obtained from fully periodic FFT. [more]
At finite temperatures lattice vibrations and magnetic fluctuations are coexisting. To study potential coupling effects, a method is required, which considers both, the spin and the lattice degrees of freedom, simultaneously. We develop and implement such a method by combining atomistic spin dynamics with ab initio molecular dynamics.

Spin-lattice coupling

At finite temperatures lattice vibrations and magnetic fluctuations are coexisting. To study potential coupling effects, a method is required, which considers both, the spin and the lattice degrees of freedom, simultaneously. We develop and implement such a method by combining atomistic spin dynamics with ab initio molecular dynamics. [more]
Modern CPUs provide a number of features to increase the computational power. Unfortunately, this increased computing power is often not used in practice, because the CPU can process the data more quickly than the memory can deliver it. To make full use of this enhanced computing power, the existing algorithms need to be revised to better exploit the computing power by exposing hidden parallelism to the CPU and improving the data locality in the data access patterns. We identified key routines in our plane-wave DFT code that offer such tuning opportunities and demonstrate a significant speed-up over standard approaches.

Optimized numerical algorithms for S/PHI/nX

Modern CPUs provide a number of features to increase the computational power. Unfortunately, this increased computing power is often not used in practice, because the CPU can process the data more quickly than the memory can deliver it. To make full use of this enhanced computing power, the existing algorithms need to be revised to better exploit the computing power by exposing hidden parallelism to the CPU and improving the data locality in the data access patterns. We identified key routines in our plane-wave DFT code that offer such tuning opportunities and demonstrate a significant speed-up over standard approaches. [more]
We have developed a MO projector scheme to apply Hubbard-U corrections within density-functional theory to molecular orbitals (MOs).

Hubbard-U corrections for Molecular Orbitals

We have developed a MO projector scheme to apply Hubbard-U corrections within density-functional theory to molecular orbitals (MOs). [more]
We have extended the sxdefectalign correction scheme to account for charged defects located at surfaces or interfaces. The scheme allows to extrapolate the formation energy of the defect from very small supercells, even if artificial fields in the calculation are sizeable.

Surface charge corrections

We have extended the sxdefectalign correction scheme to account for charged defects located at surfaces or interfaces. The scheme allows to extrapolate the formation energy of the defect from very small supercells, even if artificial fields in the calculation are sizeable. [more]
Self-healing metallic materials for the practical use are not properly developed despite of their numerous potential applications. We investigate the possibility of designing new self-healing metals by using a hierarchical modeling approach. The present study aims at examining the interaction between nano-cracks and shape memory nano-particles which is an important concept to realize self-heling metals. The knowledge gained from the present study will guide future experimental works.

Atomic scale investigation of self-healing mechanisms in metallic materials

Self-healing metallic materials for the practical use are not properly developed despite of their numerous potential applications. We investigate the possibility of designing new self-healing metals by using a hierarchical modeling approach. The present study aims at examining the interaction between nano-cracks and shape memory nano-particles which is an important concept to realize self-heling metals. The knowledge gained from the present study will guide future experimental works. [more]
 
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