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### Browsing by Author "Janovec, Václav"

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- ItemCoset Decompositions of Space Groups: Applications to Domain Structure Analysis(Munksgaard Int Publ Ltd, 1997) Dirl, R.; Zbinbr, P.; Davies, Brian L.; Janovec, Václav
Show more Left- and double-coset decompositions of space groups are systematically analysed by putting the emphasis on the introduction of special auxiliary groups. An algorithm is tailored to exploit the specific structure of space groups. The new results are, amongst others, an efficient alternative method to determine for space groups minimal sets of double-coset representatives and a general formula that gives the structure and number of left cosets that are contained in double cosets. Left-coset and double-coset decompositions of space groups are exploited in domain structure analysis.Show more - ItemExamination of point group symmetries of non-ferroelastic domain walls(Taylor & Francis Ltd, 1997) Přívratská, Jana; Janovec, Václav
Show more We recall how the symmetry properties of planar walls can be derived and how the orientational dependences of domain wall symmetry are related to simple crystal forms used in crystal morphology. We present a sample page of tables that contain symmetry properties of all crystallographically different non-ferroelastic domain walls in continuum description and on simple examples demonstrate how they can be used in discussing tensor properties of non-ferroelastic domain walls.Show more - ItemLayer groups, scanning tables and the structure of domain walls(Taylor & Francis Ltd, 1997) Janovec, Václav; Kopský, Vojtěch
Show more Symmetry of possible domain walls of orientations (111) and (100) in fulleren is considered as an example of the use of scanning tables which should appear in a scheduled Vol. E: “Subperiodic Groups” of the International Tables for Crystallography. Fullerene molecules have icosahedral symmetry. Possible orientation states of molecules of C 60, compatible with the symmetry Pa , are those in which one of the three-fold axes of icosahedron coincides with one of the cubic threefold axes. The orientation in each position is characterized by an angle ø by which it deviates from the orientation in which the icosahedral mirror planes passing through the axes also coincide with respective cubic mirror planes. Domain states and domain pairs are described in terms of these orientations. There exist only two sets of equivalent domain pairs; a translational pair with symmetry Cmce and a rotational pair with symmetry R m. Sectional layer groups of these space symmetries are determined with use of scanning tables. These layer groups determine the site point symmetries in respective walls and hence the possible orientation states of C 60 molecules within the wall as well as their modulation towards the region of domain states.Show more - ItemPC software for crystallographic space groups and its application in symmetry analysis of domain structures(Taylor & Francis Ltd, 1997) Davies, Brian L.; Dirl, R.; Janovec, Václav; Zikmund, Zdeněk
Show more An integrated package of programs has been developed to investigate the structures and representations of crystallographic space groups. The programs, written in PASCAL and C, are made user friendly by additional programs using the Oakland C-scape Interface Management System. A Microsoft Windows version of the software is currently being developed using Borland Delphi. For a given phase transition the software identifies all domain states and finds inter alia (i) symmetry groups of all domain states in algebraic form as a conjugate subgroup stratum, (ii) all operations that transform a given domain state into another domain state, (iii) classes of crystallographically equivalent domain pairs, (iv) symmetry groups of ordered and unordered domain pairs. As an illustrative example software results for the triply commensurate charge-density-wave domain states in the 2H polytype TaSe 2 are presented.Show more - ItemPyromagnetic domain walls connecting antiferromagnetic non-ferroelastic magnetoelectric domains(Taylor & Francis Ltd, 1997) Přívratská, Jana; Janovec, Václav
Show more We describe a group-theoretical procedure that enables one to find necessary conditions for the appearance of spontaneous magnetization in domain walls. We illustrate the derivation of wall symmetries on example of Cr2O3 and present a brief summary of a systematic analysis of domain walls in antiferromagnetic non-ferroelastic and magnetoelectric phases which shows that in more than 50% of possible domain walls a spontaneous magnetization may appear.Show more - ItemA sample analysis of domain walls in simple cubic phase of C60(Taylor & Francis Ltd, 1997) Saint-Grégoire, Pierre; Janovec, Václav; Kopský, Vojtěch
Show more An analysis of possible structure of a domain wall (111) in rotational twin of fullerene C 60 is performed with use of sectional layer groups. The eight possible domain states are described and it is shown that there exist only two types of domain pairs among the 46 possible combinations; one translational and one rotational. Possible orientation states of fullerene molecules in microscopic structure of the domain wall with orientation (111) are deduced.Show more - ItemSymmetry properties of domain structures(Technická Univerzita v Liberci, ) Janovec, Václav
Show more - ItemTensor distinction of domains resulting from non-ferroelastic transitions to subgroups of index n > 2(Taylor & Francis Ltd, 1997) Litvin, Daniel B.; Janovec, Václav
Show more The method of determining the tensor distinction of domains resulting from non-ferroelastic phase transitions from a high symmetry phase of symmetry G to a low symmetry phase of symmetry F of index n = 2 in G (V. Janovec, L. Richterova, and D.B. Litvin, Ferroelectrics 40, 95 (1993)) is extended to the general case of index n>2. For all cases where n>2, a tabulation is given of important physical property tensors which can distinguish between domains. This includes both physical property tensors associated with a primary order parameter which can distinguish between all domains, and those associated with secondary order parameters which can distinguish between some but not all domains.Show more