Dr. Matthias Posselt
Phone: +49 351 260 3279
+49 351 260 2199

Computer Simulations

In order to get a better understanding of atomic-level dynamics, kinetics and thermodynamics in solids under particle irradiation and/or thermal and mechanical load,  atomistic simulations are performed. The main focus is on investigations of iron-based alloys and semiconductor materials.

Research subjects:

  • Thermodynamics and kinetics of defects; Irradiation-induced defect formation
  • Formation and properties of nanoclusters embedded in solids
  • Ion-beam mixing of Si- and Ge-multilayers
  • Epitaxial recrystallization of amorphous Si and Ge layers


  • First-Principle Simulations
  • Molecular Dynamics
  • Monte-Carlo Simulations
  • Binary Collision Simulations
Energy_barriers_XW_MP ©Copyright: Dr. Posselt, Matthias

Fig. 1: Energy barriers an oxygen atom has to overcome during the diffusion in pure iron (green dashed line), and in the environment of a foreign titanium atom (black solid line). The numbers denote the possible neighbour positions of oxygen (red) relative to titanium (green). Due to the strong binding at the first and second neighbour position the oxygen diffusion slows down remarkably. This was also verified by the calculation of the diffusion coefficient by Atomistic Kinetic Monte Carlo simulations [X. Wang, M. Posselt, J. Faßbender, Phys. Rev. B 98 (2018) 064103].

Free_energy_MP ©Copyright: Dr. Posselt, Matthias

Fig. 2: Contributions of phonon excitations or lattice vibrations (thick line) and of the sum of phonon and electron (thin line) excitations to the free binding energy of vacancy and copper clusters vs. temperature. Since positive/negative energy means repulsion/attraction the combined effect of phonon and electron excitations leads to a loss of stability of the clusters with increasing temperature. At 1000 K this loss (related to the ground state binding energy)  is about 14 and 18% for v3 and v4, respectively,  and for Cu3 and Cu4 it is 36 and 45%, respectively [M. Posselt, M.  Devaraj, M. Schiwarth, Comput. Mater. Sci. 127 (2017) 284].

Present group members: Dr. Matthias Posselt, Xiaoshuang Wang, Muthu Vallinayagam

Publications since 2015:

S. B. Sruthil Lal, D. Murali, M. Posselt, A. Sharan: Accurate determination of quasi-particle electronic and optical spectra of anatase titanium dioxide, AIP Conf. Proc. 2265 (2020) 030375

S. Prucnal, M. O. Liedke, X. Wang, M. Butterling, M. Posselt, J. Knoch, H. Windgassen, E. Hirschmann, Y. Berencen, L. Rebohle, M. Wang, E. Napoltani, J. Frigerio, A. Ballabio, G. Isella, R. Hübner, A. Wagner, H. Bracht, M. Helm, S. Zhou: Dissolution of donor-vacancy clusters in heavily doped n-type germanium, New Journal of Physics (2020), Online First (2020) DOI: 10.1088/1367-2630/abc466

D. Radić, S. Hilke, M. Peterlechner, M. Posselt, G. Wilde, H. Bracht:  Comparison of experimental STEM conditions for fluctuation electron microscopy, Microscopy and Microanalysis, First view, DOI:

X. Wang, J. Faßbender, M. Posselt: Mutual dependence of oxygen and vacancy diffusion in bcc Fe and dilute iron alloys, Phys. Rev. B 101 (2020) 174107

M. Posselt (Editor): Special Issue "First-Principle and Atomistic Modelling in Materials Science", Materials (2019-2020)

N. Raja, D. Murali, S. V. M. Satyanarayana, M. Posselt: First principles calculations of the thermodynamic stability of Ba, Zr, and O vacancies in BaZrO3, RSC Adv. 9 (2019) 34158

D. Radic, S. Hilke, M. Peterlechner, M. Posselt, H. Bracht: Fluctuation electron microscopy on silicon amorphized at varying self ion-implantation conditions, J. Appl. Phys. 126 (2019) 095707

M. Vallinayagam, M. Posselt, J. Faßbender: Interaction of O–Y and O–Y–Ti clusters embedded in bcc Fe with He, vacancies and self-interstitial atoms, J. Phys.: Condens. Matter 31 (2019) 485702

X. Wang, J. Faßbender, M. Posselt: Efficient calculation methods for the diffusion coefficient of interstitial solutes in dilute alloys, Materials 12 (2019) 1491

M. Vallinayagam, M. Posselt, J. Faßbender: Investigation of structural models for O–Y and O–Y–Ti clusters in bcc Fe: a density functional theory study, J. Phys.: Condens. Matter 31 (2019) 095701

X. Wang, M. Posselt, J. Faßbender: Influence of substitutional atoms on the diffusion of oxygen in dilute iron alloys, Phys. Rev. B 98 (2018) 064103

A. T. Al Motasem, M. Posselt, J. Bergström: Nanoindentation and nanoscratching of a ferrite/austenite iron bi-crystal: An atomistic study, Tribol. Int. 127 (2018) 231

J. Kirschbaum, T. Teuber, A. Donner, M. Radek, D. Bougeard, R. Böttger, J. Lundsgaard Hansen, A. Nylandsted Larsen, M. Posselt*, H. Bracht*: Self-diffusion in amorphous silicon by local bond rearrangements, Phys. Rev. Lett 120 (2018) 225902

G. Bonny, A. Bakaev, D. Terentyev, E. Zhurkin, M. Posselt: Atomistic study of the hardening of ferritic iron by Ni-Cr decorated dislocation loops, J. Nucl. Mater. 498 (2018) 430

A. Bakaev, D. Terentyev, Z. Chang, M. Posselt, P. Olsson, E. E. Zhurkin: Effect of isotropic stress on dislocation bias factor in bcc iron: an atomistic study, Phil. Mag. 98 (2018) 54

N. Raja, D. Murali, M. Posselt, M. S. V. M.  Satyanarayana: High temperature stability of BaZrO3: An ab initio thermodynamic study, Phys. Stat. Sol. B 2017, 254, 1700398

M. Radek, B. Liedke, B. Schmidt, M. Voelskow, L. Bischoff, J. L. Hansen, A. N. Larsen, D. Bougeard, R. Böttger, S. Prucnal, M. Posselt, H. Bracht: Ion-beam-induced atomic mixing in Ge, Si, and SiGe, studied by means of isotope multilayer structures, Materials 10 (2017) 813

M. Posselt, M.  Devaraj, M. Schiwarth: Influence of phonon and electron excitations on the free energy of defect clusters in solids: A first-principles study, Computational Materials Science 127 (2017) 284

G. Bonny, A.  Bakaev, P. Olsson, C. Domain, E.  E. Zhurkin, M. Posselt.: Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels, J. Nucl. Mater. 484 (2017) 42

A. Bakaev, D. Terentyev, P. Grigorev, M. Posselt, E. E. Zhurkin: Ab intitio study of interaction of helium with edge and screw dislocations in tungsten, Nucl. Instr. Meth. B 393 (2017) 150

M. Radek,  H. Bracht,  B. Liedke, R. Böttger, M. Posselt: Ion-beam induced atomic mixing in isotopically controlled silicon multilayers, J. Appl. Phys. 120 (2016) 185701

A. T. Al-Motasem, N. T.  Mai, S. T.  Choi, M. Posselt: Atomistic study on mixed-mode fracture mechanisms of ferrite iron interacting with coherent copper and nickel nanoclusters, J. Nucl. Mater. 472 (2016) 20

D. Murali, M. Posselt,  M. Schiwarth: First-principles calculation of defect free energies: General aspects illustrated in the case of bcc Fe, Phys. Rev. B 92 (2015) 064103

M. Radek, H. Bracht, B. C. Johnson, J. C. McCallum,  M. Posselt, B. Liedke: Atomic transport during solid-phase epitaxial recrystallization of amorphous germanium, Appl. Phys. Lett. 107 (2015) 082112

Roisin A. Kelly, Bartosz Liedke, Stefan Baldauf, Anushka Gangnaik, Subhajit Biswas,Yordan Georgiev, Justin D. Holmes, Matthias Posselt, Nikolay Petkov: Epitaxial Post-Implant Recrystallization in Germanium Nanowires, Cryst. Growth Des.15 ( 2015) 4581

Shengqiang Zhou, Fang Liu, S. Prucnal, Kun Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, M. Helm: Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy, Sci. Rep. 5 (2015) 8329


Dr. Matthias Posselt
Phone: +49 351 260 3279
+49 351 260 2199