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Karlsruhe Institute of Technology

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Das KIT ist seit 2010 als familiengerechte Hochschule zertifiziert.
Lars Pastewka

Prof. Dr. Lars Pastewka

[sci.] professor for simulation at the University Freiburg
Material science
simulation of interfaces

Group: [prev.] Emmy Noether
Room: Germany, Freiburg
lars pastewkaAcg1∂imtek uni-freiburg de


IMTEK - Department of Microsystems Engineering
Laboratory for Simulation

Georges-Koehler-Allee 103-03
D-79110 Freiburg
Germany



Research

The group has moved to the Department of Microsystems Engineering at the University of Freiburg.

Our research revolves around computer modeling of mechanical and chemical properties of material interfaces and their interaction with fluids and other solids. We have a particular focus on tribological phenomena (contact, adhesion, friction, lubrication, wear) that naturally occur at interfaces. Such processes are important in macro- and microsystems and their control is decisive for the lifetime of a device. For example in miniaturized components that have a high surface to volume ratio, interfacial processes can entirely dominate mechanical behavior: At small scales, strength is determined by surface and not bulk defects, the flow of liquids through nanochannels can be controlled by surface topography and chemistry and surface forces such as adhesion and friction can overcome body forces and lead to stiction. Common to these phenomena is the interplay of local chemistry, long-ranged interaction (such as elasticity) and geometrical disorder (such as surface roughness). Models at atomic, mesoscopic and macroscopic scales are therefore required for their understanding.

Multiasperity contact and adhesion. Contact, friction and wear of natural and engineered surfaces cannot be understood without consideration of surface roughness. Roughness limits the area of intimate atomic contact to isolated areas where summits (asperities) meet and hence where the process zone develops. We use large scale contact mechanical calculations at mesoscopic and continuum sclaes to study the influence of surface topography on macroscopic properties such as contact stiffness, adhesion and friction.

Representative publication: PNAS 111, 3298 (2014)

Single-asperity contact and adhesion. Spherical objects, such as tips on an atomic-force microscope (AFM), are often used as simplifying models for the contact of a single asperity in a rough contact. AFM experiments are carried out at scales that are in principle accessible by molecular simulations. We carry out such calculations to aid the interpretation of experimental AFM friction, topography and adhesion data.

Representative publication: Nano Lett. 14, 7145 (2014)

Shear-induced melting and solid state amorphization. Mechanically sheared systems can undergo structural transitions. Examples are colloidal crystals that shear-melt or the solid state amorphization of diamond or silicon during tribological loading. Such disordered phases often appear on tribologically loaded interface and it is believe that they constitute a form of solid lubricant. We use molecular dynamics calculations of simple model materials to study the formation of glasses during mechanical shear.

Representative publication: Nature Materials 10, 34 (2011)

Mechanics of amorphous materials. Motivated by the above, we are also interested in the mechanical behavior of traditional bulk amorphous materials. These deform in localized rearrangements of regions of ~100 atoms, so called shear transformations, which coalesce into shear bands on long time scales. We study the deformation of network and metallic glasses in molecular dynamics calculations.

Representative publication: Tribol. Lett. 53, 119 (2014)

Lubrication. Liquids are ubiquitously used to reduce friction and wear in machinery. We use molecular dynamics calculation to study simple lubricants in confined dimensions and the effect of surface topography and surface chemistry on their flow. We are particularly interested in squeeze out of lubricant and the transition from lubricated to solid contact under boundary lubrication conditions.

Representative publication: Science Advances 2, e1501585 (2016)

Contact Mechanics

Contact Mechanics
type: Vorlesung (V)
semester: WS 15/16
time: 2015-10-20
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3


2015-10-27
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-11-03
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-11-10
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-11-17
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-11-24
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-12-01
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-12-08
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-12-15
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2015-12-22
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2016-01-12
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2016-01-19
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2016-01-26
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2016-02-02
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3

2016-02-09
09:45 - 11:15 wöchentlich
Geb. 10.91, Raum 227/3


lecturer: Dr. Lars Pastewka
sws: 2
lv-no.: 2181220
Prerequisites

none

Recommendations:

preliminary knowledge in mathematics, physics and materials science

Bibliography

K. L. Johnson, Contact Mechanics (Cambridge University Press, 1985)

D. Maugis, Contact, Adhesion and Rupture of Elastic Solids (Springer-Verlag, 2000)

J. Israelachvili, Intermolecular and Surface Forces (Academic Press, 1985)

Content of teaching

The course introduces contact mechanics of smooth and rough surface for non-adhesive and adhesive interfacial conditions. There will a computer lab held in parallel to the lecture that teaches numerical approaches to contact mechanical problems.

  1. Introduction: contact area and stiffness
  2. Theory of the elastic half-space
  3. Contact of nonadhesive spheres: Hertz theory
  4. Physics and chemistry of adhesive interactions at interfaces
  5. Contact of adhesive spheres: theories of Johnson-Kendall-Roberts, Derjaguin-Muller-Toporov and Maugis-Dugdale
  6. Surface roughness: topography, power spectral density, structure of real surfaces, fractal surfaces as a model, metrology
  7. Contact of nonadhesive rough surfaces: theories of Greenwood-Williamson, Persson, Hyun-Pei-Robbins-Molinari
  8. Contact of adhesive rough surface: theories of Fuller-Tabor, Persson and recent numerical results
  9. Contact of rough spheres: theory of Greenwood-Tripp and recent numerical results
  10. Lateral and sliding contact: theories of Cattaneo-Mindlin, Savkoor, Persson
  11. Applications of contact mechanics
Workload

regular attendance: 22,5 hours

self-study: 97,5 hours

Aim

The student

  • knows models for smooth and rough surfaces under non-adhesive and adhesive conditions and understands their strengths and limits
  • knows fundamental scaling relations for the functional dependency between contact area, stiffness and normal force
  • can apply numerical methods to study questions from materials science
Exam description

oral exam 30 minutes

Atomistic simulations and molecular dynamics

Atomistic simulations and molecular dynamics
type: Vorlesung (V)
semester: SS 2016
time: 2016-04-21
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II


2016-04-28
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-05-12
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-05-19
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-06-02
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-06-09
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-06-16
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-06-23
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-06-30
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-07-07
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-07-14
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II

2016-07-21
09:45 - 11:15 wöchentlich
10.50 HS 101 10.50 Kollegiengebäude Bauingenieure II


lecturer:

Dr. Lars Pastewka

sws: 2
lv-no.: 2181740
Notes

Lecture in English!

Prerequisites

compulsory preconditions: none

Recommendations:

preliminary knowlegde in mathematics, physics and materials science

Bibliography
  1. Understanding Molecular Simulation: From Algorithms to Applications, Daan Frenkel and Berend Smit (Academic Press, 2001)
  2. Computer simulation of liquids, M. P. Allen and Dominic J. Tildesley (Clarendon Press, Oxford, 1996)
Content of teaching

The lecture introduces the foundation of particle based simulation methods focussing on molecular dynamics:

1. Introduction
2. Physics of Materials
3. MD Basics, Atom-Billard
* particle, position, energy, forces, pair potentials
* initial and boundary conditions
* time integration
4. algorithms
5. statics, dynamics, thermodynamics
6. MD output
7. interaction between particles
* pair potential -- many body potentials
* principles of quantum mechanics
* tight binding methods
* dissipative particle dynamics
8. application of particle based methods

Workload

regular attendance: 22,5 hours
exercise: 22,5 hours
self-study: 75 hours

Aim

The student can

  • describe the physical foundation of particle based simulation method (e.g. molecular dynamics)
  • apply particle based simulation methods to problems in materials science
Exam description

oral exam 30 minutes

Publications

A current list of publications can also be found on Google Scholar and Researcher ID.

2016

Quantitative characterization of surface topography using spectral analysis
T. Jacobs, T. Junge, L. Pastewka
arXiv:1607.03040 (2016)

Offset-corrected delta-Kohn-Sham scheme for the semi-empirical prediction of absolute X-ray photoelectron energies in molecules and solids
M. Walter, M. Moseler, L. Pastewka
Phys.
 Rev. B 94, 041112(R) (2016)

Molecular dynamic simulation of collision-induced third-body formation in hydrogen-free diamond-like Carbon asperities
J. von Lautz, L. Pastewka, P. Gumbsch, M. Moseler
Tribol. Lett. 63, 26 (2016)

Contact area of rough spheres: Large scale simulations and simple scaling laws
L. Pastewka, M.O. Robbins
Appl. Phys. Lett. 108, 221601 (2016)

Elasticity limits structural superlubricity in large contacts
T.A. Sharp, L. Pastewka, M.O. Robbins
Phys. Rev. B 93, 121402(R) (2016)

Boundary lubrication of heterogeneous surfaces and the onset of cavitation in frictional contacts
D. Savio, L. Pastewka, P. Gumbsch
Science Advances 2, e1501585 (2016)

Reibung unter Zugzwang
L. Pastewka
Physik Journal 15, 16 (2016)

Activation and mechanochemical breaking of C-C bonds initiate wear of diamond (110) surfaces in contact with silica
A. Peguiron, G. Moras, M. Walter, H. Uetsuka, L. Pastewka, M. Moseler
Carbon 98, 474 (2016)

2015

Low speed crack propagation via kink formation and advance on the silicon (110) cleavage plane
J.R. Kermode, A. Gleizer, G. Kovel, L. Pastewka, G. Csányi, D. Sherman, A. De Vita
Phys. Rev. Lett. 115, 135501 (2015)

Energy filtering transmission electron microscopy and atomistic simulations of tribo-induced hybridization change of nanocrystalline diamond coating
M.I. De Barros Bouchet, C. Matta, B. Vacher, Th. Le-Mogne, J.M. Martin, J. von Lautz, T. Ma, L. Pastewka, J. Otschik, P. Gumbsch, M. Moseler
Carbon 87, 317 (2015)

2014

Atomic scale mechanisms of friction reduction and wear protection by graphene
A. Klemenz, L. Pastewka, S.G. Balakrishna, A. Caron, R. Bennewitz, M. Moseler
Nano Lett. 14, 7145 (2014)

Surface passivation and boundary lubrication of self-mated tetrahedral amorphous carbon asperities under extreme tribological conditions
P.A. Romero, L. Pastewka, J. von Lautz, M. Moseler
Friction 2, 193 (2014)

Contact between rough surfaces and a criterion for macroscopic adhesion
L. Pastewka, M.O. Robbins
PNAS 111, 3298 (2014)

SYMPLER: SYMbolic ParticLE simulatoR with grid-computing interface
D. Kauzlarić, M. Dynowski, L. Pastewka, A. Greiner, J.G. Korvink
Comp. Phys. Comm. 185, 1085 (2014)

Wear, plasticity, and rehybridization in tetrahedral amorphous carbon
T. Kunze, M. Posselt, S. Gemming, G. Seifert, A.R. Konicek, R.W. Carpick, L. Pastewka, M. Moseler
Tribol. Lett. 53, 119 (2014)

2013

Comment on “Friction between a viscoelastic body and a rigid surface with random self-affine roughness”
I.A. Lyashenko, L. Pastewka, B.N.J. Persson
Phys. Rev. Lett. 111, 189401 (2013)

On the validity of the method of reduction of dimensionality: area of contact, average interfacial separation and contact stiffness
I.A. Lyashenko, L. Pastewka, B.N.J. Persson
Tribol. Lett. 52, 223 (2013)

Lithium chalcogenidotetrelates: LiChT – Synthesis and characterization of new Li+ ion conducting Li/Sn/Se compounds
T. Kaib, P. Bron, S. Haddadpour, L. Mayrhofer, L. Pastewka, T.T. Järvi, M. Moseler, B. Roling, S. Dehnen
Chem. Mater. 25, 2961 (2013)

Finite-size scaling in the interfacial stiffness of rough elastic contacts
L. Pastewka, N. Prodanov, B. Lorenz, M.H. Müser, M.O. Robbins, B.N.J. Persson
Phys. Rev. E 87, 062809 (2013)

Screened empirical bond-order potentials for Si-C
L. Pastewka, A. Klemenz, P. Gumbsch, M. Moseler
Phys. Rev. B 87, 205410 (2013)

Li+ adsorption at prismatic graphite surfaces enhances interlayer cohesion
L. Pastewka, S. Malola, M. Moseler, P. Koskinen
J. Power Sources 239, 321 (2013)

Adaptive molecular decomposition: Large scale quantum chemistry for liquids
T.T. Järvi, L. Mayrhofer, J. Polvi, K. Nordlund, L. Pastewka, M. Moseler
J. Chem. Phys. 138, 104108 (2013)

Experimental and numerical atomistic investigation of the third body formation process in dry tungsten/tungsten-carbide tribo couples
P. Stoyanov, P.A. Romero, T.T. Järvi, L. Pastewka, M. Scherge, P. Stemmer, A. Fischer, M. Dienwiebel, M. Moseler
Tribol. Lett. 50, 67 (2013)

2012

Seamless elastic boundaries for atomistic calculations
L. Pastewka, T.A. Sharp, M.O. Robbins
Phys. Rev. B 86, 075459 (2012)

Bond-order potentials for fracture, wear, and plasticity
L. Pastewka, M. Mrovec, M. Moseler, P. Gumbsch
MRS Bulletin 37, 493 (2012)

2011

Progressive shortening of sp-hybridized carbon chains through oxygen-induced cleavage
G. Moras, L. Pastewka, M. Walter, J. Schnagl, P. Gumbsch, M. Moseler
J. Phys. Chem. C 115, 24653 (2011)

Formation and oxidation of linear carbon chains and their role in the wear of carbon materials
G. Moras, L. Pastewka, P. Gumbsch, M. Moseler
Tribol. Lett. 44, 355 (2011)

Revised periodic boundary conditions: Fundamentals, electrostatics, and the tight-binding approximation
O.O. Kit, L. Pastewka, P. Koskinen
Phys. Rev. B 84, 155431 (2011)

Smoothed particle hydrodynamics simulation of shear-induced powder migration in injection moulding
D. Kauzlarić, L. Pastewka, H. Meyer, R. Heldele, M. Schulz, O. Weber, V. Piotter, J. Hausselt, A. Greiner, J.G. Korvink
Phil. Trans. Roy. Soc. A 369, 2320 (2011)

Charge-transfer model for carbonaceous electrodes in polar environments
L. Pastewka, T.T. Järvi, L. Mayrhofer, M. Moseler
Phys. Rev. B 83, 165418 (2011)

Anisotropic mechanical amorphization drives wear in diamond
L. Pastewka, S. Moser, P. Gumbsch, M. Moseler
Nature Mater. 10, 34 (2011)

2010

Molecular dynamics simulation of gold solid film lubrication
L. Pastewka, J. Peguiron, P. Gumbsch, M. Moseler
Int. J. Mater. Res. 101, 981 (2010)

Atomistic insights into the running-in, lubrication, and failure of hydrogenated diamond-like carbon coatings
L. Pastewka, S. Moser, M. Moseler
Tribol. Lett. 39, 49 (2010)

2009

Understanding the microscopic processes that govern the charge-induced deformation of carbon nanotubes
L. Pastewka, P. Koskinen, C. Elsässer, M. Moseler
Phys. Rev. B 80, 155428 (2009)

Surface amorphization, sputter rate, and intrinsic stresses of silicon during low energy Ga+ focused-ion beam milling
L. Pastewka, R. Salzer, A. Graff, F. Altmann, M. Moseler
Nucl. Instrum. Meth. B 267, 3072 (2009)

2008

Describing bond-breaking processes by reactive potentials: the importance of an environment-dependent interaction range
L. Pastewka, P. Pou, R. Pérez, P. Gumbsch, M. Moseler
Phys. Rev. B 78, 161402(R) (2008)

The running-in of amorphous hydrocarbon tribocoatings: a comparison between experiment and molecular dynamics simulations
L. Pastewka, S. Moser, M. Moseler, B. Blug, S. Meier, T. Hollstein, P. Gumbsch
Int. J. Mater. Res. 99, 1136 (2008)

Integrated process simulation of primary shaping: multi scale approaches
D. Kauzlarić, J. Lienemann, L. Pastewka, A. Greiner, J.G. Korvink
Microsyst. Technol. 14, 1789 (2008)

2006

Thermostat with a local heat-bath coupling for exact energy conservation in dissipative particle dynamics
L. Pastewka, D. Kauzlarić, A. Greiner, J.G. Korvink
Phys. Rev. E 76, 037701 (2006)

Read-out concepts for multiplexed bead-based fluorescence immunoassays on centrifugal microfluidic platforms
L. Riegger, M. Grumann, T. Nann, J. Riegler, O. Ehlert, W. Bessler, K. Mittenbühler, G. Urban, L. Pastewka, T. Brenner, R. Zengerle, J. Ducrée
Sens. Actuat. A-Phys. 126, 455 (2006)

2005

Parallelization of chip-based fluorescence immuno-assays with quantum-dot labeled beads
M. Grumann, L. Riegger, T. Nann, J. Riegler, O. Ehlert, K. Mittenbühler, G. Urban, L. Pastewka, T. Brenner, R. Zengerle, J. Ducreé
Proc. Transducers 1114 (2005)

2004

Capacitance, induced charges, and bound states of biased carbon nanotube systems
P. Pomorski, L. Pastewka, C. Roland, H. Guo, J. Wang
Phys. Rev. B 69, 115418 (2004)

Quantum calculations of carbon nanotube charging and capacitance
P. Pomorski, L. Pastewka, C. Roland, H. Guo, J. Wang
Mat. Res. Soc. Symp. Proc. N3.6.1 (2004)

Software

We are actively developing open-source academic simulation tools.

Atomistica

Atomistica is a library of interatomic potentials for use with LAMMPS and ASE, two widely used simulation environments for atomic-scale simulations such as molecular dynamics. Atomistica is developed in collaboration with the group of Michael Moseler at Fraunhofer IWM.

matscipy

matscipy is a library of utility function for fracture and contact mechanical problems based on ASE. matscipy is developed in collaboration with James Kermode at Warwick University.

USER-GFMD

USER-GFMD is a plugin for the widely used molecular dynamics code LAMMPS that implements Green's function molecular dynamics. USER-GFMD is developed with the group of Mark Robbins at Johns Hopkins University.

NetCDF trajectory file format

We are maintaining input and ouput modules for molecular dynamics trajectory files in the AMBER NetCDF trajectory format. Modules are available for ASE, LAMMPS and Ovito.

SYMPLER

SYMPLER is an SPH/DPD simulation environment with a flexible handling of interaction laws. Interaction laws are entered in the form of compact expression in the input file rather than being hard-wired into the code. SYMPLER is maintained by David Kauzlaric.