SVIBOR - Project code: 1-03-066

MINISTRY OF SCIENCE AND TECHNOLOGY

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Project code: 1-03-066


VIBRATIONAL PHENOMENA AND INTERACTIONS IN CONDENSED MATTER


Main researcher: FURIĆ, KREŠIMIR (12661)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/31/93.
Papers on project (total): 129
Papers on project quoted in Current Contents: 57
Institution name: Institut "Ruđer Bošković", Zagreb (98)
Department/Institute: Department of Physics, Molecular Physics Laboratory
Address: Bijenička cesta 54, P.P. 1016
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (01) 4561-020
Fax: 385 (01) 434-467
E-mail: KFURIC@OLIMP.IRB.HR
Summary: The subject of this project touches several fields of physics which are close to chemistry, such as molecular sciences, solid state physics and material science. The basic experimental and computational methods are mostly vibrational and spectroscopic. Using Raman and infrared spectroscopy the state of the matter is studied in all phases in dependence on some external parameter (temperature, pressure or concentration). Special attention is paid to phase transitions and to atom-atom interactions which result with strongly anharmonic functions/surfaces. The effects of the laser beam-material interactions are investigated up to the breakdown of surfaces, especially in the case of metals and amorphous semiconductors. We are using molecular dynamics computer simulation methods to investigate structural, dynamical and electronic properties of metal surfaces. The published articles are in a domain of fundamental research, but offer the possibility of development and application.

Keywords: vibrational spectroscopy (Raman and infrared), vibrational analysis, phase transitions, molecular crystals, amorphous materials, laser-material interactions, molecular dynamics simulation

Research goals: Scientific activity within this project is partly acontinuation of the research of molecular dynamics in solid,liquid and gaseous phases. Using vibrational spectroscopy methodsas a primary tool some small molecules, benzene derivatives andcarboxylic acids, have been studied. At the same time thecalculations which give us the deeper insight of both inter- and intra-molecular interactions have been performed. Stronganharmonical vibrations, e.g. the case of hindered rotation or inversion in a double-well potential, are recognised and extracted out of the complete spectra, and are extensively studied. The comparative analysis of benzophenone and some parasubstituted derivatives has led to the recognition of the influence of substituted atom on the characteristical ring vibrations. The phase transitions have been investigated invarious halogenated benzophenone crystals. The commensurate-incommensurate phase transition has been observed as a function of pressure and temperature and treated in the crystal of ammonium oxalate semihydrate. Low frequency modes, i.e. the lattice vibrations have been investigated in cytosine monohydrate crystal. In dicyclopropylacetylene various stable and unstable phases have been observed.Isotropic and anisotropic parts of a Raman band which arecharacteristic for the water molecule bending have been analysed using Fourier deconvolution method. The dependence of the profileof some vibrational bands on the concentration of the solutionhas been explained within the Fermi resonance model with theassumption of weak hydrogen bonding. The development of the calculation method for the latticevibrations of semi-rigid molecules has been continued. Thecomplete analysis of normal coordinates for some halogenatedbenzophenones has been carried out. Using this method a number ofcyclopropyl derivatives have been studied, and the stableconformation for one of them has been established. The earlierdeveloped method for solving the time dependent Schroedingerequation (TDRH) has been improved with a new form for the wavefunction. The superconductivity phenomenon has been investigatedunder the assumption of a strong magnetic field within the BCStheory and QLA approximation. The effects of laser-material interaction have been studiedin two directions: (i) The breakdown of the surface of refractive metals,corresponding types and systematization of breakdown structures.For the first time the systematization for all observed types ofbrittle breakdown structures, which follows the principle ofincreasing topological complexity, has been suggested. Also, thesurface cavitation breakdown structures have been classifiedaccording to the configuration of the stress field at the"Y"-site. Three basic modes, named canonic, have been found. (ii) The simulation of laser oxidation has been carried out inthe linearly increasing thermal field. The oxidation process isinhomogeneous with the substantial influence of the screwdislocations as the centers of self-organized growth. It has beenoserved that the growth of the self-organized oxide structures isnon-linear and non-equilibrium process, and its type essentiallydependent on the rate of the temperature increase. The systemreacts to the continuous temperature increase with continuousformation of self-organized structures. The structure changes and vibrational phenomena of thinlayers of amorphous silica have been induced/analysed usingfocused laser beam. For the first time the Bose peak inhydrogenated amorphous silica was observed and studied. Themechanism of crystallization caused by intensive laser beam on athin layer of a-Si:H was explained. The influence of differentenvironments (H2, N2, O2) on nonstechiometry of thin films TiO2during their thermal treatment was investigated too. In otheramorphous materials such as borosilicate glasses Bose peak hasalso been studied. The work on the glassy phase of molecularcrystals which can be considered as a liquid-crystal transitionstate is in progress. We have started a new part of research dealing with molecular dynamics simulations. Modern and fast computers and algorithms give rise to very successful applications of new methods for simulation of materials. Nowa days these methods produce results comparable with the best experimental results. They are also used to investigate phenomena on the microscopic time and length scales which are not yet accessible in the laboratory. We are working on molecular dynamics simulation of phase transitions, thin film growth, interaction with laser light and vibrational phenomena for metallic surfaces.

COOPERATION - PROJECTS


  1. Name of project: Metal surface effects by pulsed CO2 laser
    Name of institution: ENEA Frascati, Enta per le Nuove Technologie, L'energia e l'ambiente
    City: Rim, Italija

  2. Name of project: Structure and vibrational dynamics of thin amorphous semiconductor films
    Name of institution: Ludwig-Maximilians-Universiteit, Sektion Physik
    City: Muenchen, Njemačka

  3. Name of project: Vibrational spectroscopy and dynamics of molecules with hydrogen bonding and/or internal rotation
    Name of institution: Ludwig-Maximilians-Universitaet, Sektion Physik
    City: Muenchen, Njemačka

  4. Name of project: Phase transitions in molecular solids
    Name of institution: Recherches Physiques, Universite Pierre et Marie Curie
    City: Pariz, Francuska
Other information about the project.
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