prof. Mgr. Miroslav Černý, Ph.D.
E-mail:   cerny.m@fme.vutbr.cz  WWW:   http://physics.fme.vutbr.cz/~mcerny/ Dept.:   Institute of Physical Engineering Dept. of Micromechanics of Materials and Engineering Acoustics Position:   Professor Room:   A2/506

Supervised courses:

• Prediction of mechanical and magnetic properties of solids from their electronic structure (DS112A)
• Physical Laboratory I (TR1)
• Physics (BF)
• Physics (BF-K)
• Prediction of mechanical and magnetic properties of solids from their electronic structure (DS112)
• Selected Chapters in Materials Science (9VFM)
• Selected Topics in Physics B (0FB)
• Solid State Physics (WFF)
• Structure and Properties of Advanced Materials (TVN)

Publications:

• ŠESTÁK, P.; ČERNÝ, M.; POKLUDA, J.:
  Energetics of NiTi allotropes under uniaxial compression
  journal article in Web of Science
• ČERNÝ, M.; ŠESTÁK, P.; ŘEHÁK, P.; VŠIANSKÁ, M.; ŠOB, M.:
  Ab initio tensile tests of grain boundaries in the fcc crystals of Ni and Co with segregated sp-impurities
  journal article in Web of Science
• ŠESTÁK, P.; ČERNÝ, M.; HE, J.; ZHANG, Z.; POKLUDA, J.:
  Multiaxial stress-strain response and displacive transformations in NiTi alloy from first principles
  journal article in Web of Science
• ŘEHÁK, P.; ČERNÝ, M.; ŠOB, M.:
  Mechanical stability of Ni and Ir under hydrostatic and uniaxial loading, IOP Publishing Ltd.
  journal article in Web of Science
• POKLUDA, J.; ČERNÝ, M.; ŠOB, M.; UMENO, Y.:
  Ab Initio Calculations of Mechanical Properties: Methods and Applications.
  journal article in Web of Science
• ČERNÝ, M.; ŠESTÁK, P.; POKLUDA, J.; ŠOB, M.:
  Shear instabilities in perfect bcc crystals during simulated tensile tests
  journal article in Web of Science
• ČERNÝ, M.; ŘEHÁK, P.; UMENO, Y.; POKLUDA, J.:
  Stability and strength of covalent crystals under uniaxial and triaxial loading from first principles
  journal article in Web of Science
• ŘEHÁK, P.; ČERNÝ, M.; POKLUDA, J.:
  Dynamic stability of fcc crystals under isotropic loading from first principles
  journal article in Web of Science
• ŠESTÁK, P.; ČERNÝ, M.; POKLUDA, J.:
  Can twinning stabilize B19' structure in NiTi martensite?, Elsevier
  journal article in Web of Science
• ČERNÝ, M.; POKLUDA, J.:
  Ideal tensile strength of cubic crystals under superimposed transverse biaxial stresses from first principles
  journal article in Web of Science
• ČERNÝ, M.; POKLUDA, J.:
  The theoretical tensile strength of fcc crystals predicted from shear strength calculations
  journal article in Web of Science

List of publications at Portal BUT

Abstracts of most important papers:

• ŠESTÁK, P.; ČERNÝ, M.; HE, J.; ZHANG, Z.; POKLUDA, J.:
  Multiaxial stress-strain response and displacive transformations in NiTi alloy from first principles
  journal article in Web of Science
  Present ab initio study was focussed on a response of NiTi martensite to a superposition of shear and tensile or compressive stresses acting normally to the shear planes. The theoretically predicted basecentered orthorhombic (BCO) ground-state structure was found unstable under uniaxial compression and two transformations, one from orthorhombic to a monoclinic symmetry and the other back from monoclinic to orthorhombic symmetry, were observed in the computational model. The former transformation shows that the uniaxial compressive stress of about 4 GPa destabilizes the BCO structure by reducing its symmetry to the experimentally observed monoclinic one. However, superposition of small shear stresses remarkably lowers the compressive stress necessary for this destabilization. The latter transformation then draws the crystal lattice to the B19 structure. The theoretical shear strength of NiTi martensite was subsequently computed as a function of the normal stress. The results obtained show that the effect of the normal stress is surprisingly opposite to that calculated for NiTi austenite and other cubic metals, i.e., that the shear strength is lowered by the compressive normal stress and vice versa.
• POKLUDA, J.; ČERNÝ, M.; ŠOB, M.; UMENO, Y.:
  Ab Initio Calculations of Mechanical Properties: Methods and Applications.
  journal article in Web of Science
  The article attempts to critically review a rather extended field of ab-initio calculations of mechanical properties of materials. After a brief description of the density functional theory and other approximations utilized in a majority of ab initio calculations, methods for predictions of elastic constants and moduli are presented. A relatively large space is devoted to computations of theoretical strength under various loading conditions. First we focus on results for perfect crystals and make an overview of advanced approaches to crystal stability. As case studies, elastic stability conditions defined according to both the adopted definition of elastic coefficients and the kind of applied loading are shown for isotropic tensile loading of molybdenum crystal and a model of microscopic deformation is illustrated for a soft phonon found in the dynamic stability analysis of isotropic loading of platinum crystal. Collected values of ideal strength under uniaxial/isotropic tension and simple shear for selected metallic and covalent crystals are discussed in terms of their comparison with available experimental data. Further attention is paid to results of studies on interfaces and grain boundaries. Applications of computed values of the moduli and the theoretical strength to prediction of intrinsic hardness and brittle/ductile behavior of crystalline materials and simulation of pop-in effect in nanoindentation tests are also included. Finally, remarks about possible topics for future ab initio studies and challenges for further development of computational methods are attached.
• ŠESTÁK, P.; ČERNÝ, M.; POKLUDA, J.:
  Can twinning stabilize B19' structure in NiTi martensite?, Elsevier
  journal article in Web of Science
  Although experimental observations determine the martensite structure of NiTi as monoclinic (B19'), abinitio calculations show that, after a full optimization of the lattice, the ideal martensite structure relaxes into orthorhombic B33 one. This paper presents a first principles investigation of the structure of (100) compound twins in martensite. The results obtained by means of two different computational codes show that the optimized structure of twin cells is very close to that of B19' martensite. This indicates that twinning can significantly contribute to mechanisms stabilizing the B19' structure in real martensite samples.
• ČERNÝ, M.; POKLUDA, J.:
  Ideal tensile strength of cubic crystals under superimposed transverse biaxial stresses from first principles
  journal article in Web of Science
  Elastic response and strength of perfect crystals is calculated for triaxial loading conditions from first principles. The triaxial stress state is constituted by uniaxial tensile stress and superimposed transverse biaxial stresses. The maximum uniaxial tensile stress is evaluated as a function of the transverse stresses. Results for eight crystals of cubic metals and two orientations <110> and <111> of the primary loading axis are presented and compared with data for <100> direction of loading. Obtained results show that, within a studied range of biaxial stresses, the maximum tensile stress monotonically increases with increasing biaxial tensile stress for most of the studied metals. Within a certain range, the dependence can be mostly approximated by a linear function.
• ČERNÝ, M.; POKLUDA, J.:
  The theoretical shear strength of fcc crystals under superimposed triaxial stress
  journal article in Web of Science
  The influence of a triaxial stress applied normally to shear planes and shear direction during affine shear deformation of fcc crystals on the theoretical shear strength is studied for the <112>{111} shear system using first principles methods. The applied relaxation procedure guarantees that the modeled system is subjected to a superposition of shear, normal and inplane stresses with individually adjustable in-plane and normal stress values. The theoretical shear strengths of individual elements prove to be qualitatively different functions of the superimposed stresses. In the special case of hydrostatic loading, however, these functions are qualitatively uniform. This behavior is discussed in terms of the electronic structure.