2/2002

Contents:

• P.K.Berzigiyarov, V.A.Zayets, I.Ya.Ginzburg, V.F.Razumov and E.F.Sheka, NANOPACK: Parallel Codes for Semiempirical Quantum-chemical Calculations of Large Systems in the sp- and spd-basis - abstract
• J.Kaczmarek, A Method of Integration of Molecular Dynamics and Continuum Mechanics for Solids - abstract
• A.Witkowska, L.Murawski and G.Bergmanski, A Molecular Dynamics Study of the Influence of Chemical Reduction on the Structure of Amorphous Germania - abstract | full text
• E.Binz and W.Schempp, Digital Information Processing: The Lie Groups defining the Filter Banks of the Compact Disc - abstract | full text
• J.K.Michalczyk and K.Murawski, Numerical Simulations of Air-pollutants in Windy Atmosphere - abstract | full text

• A.Januszajtis, Societas Physicae Experimentalis - The First Physics Society in Poland. The Origins of the Society

Abstracts:

• P.K.Berzigiyarov, V.A.Zayets, I.Ya.Ginzburg, V.F.Razumov and E.F.Sheka, NANOPACK: Parallel Codes for Semiempirical Quantum-chemical Calculations of Large Systems in the sp- and spd-basis

  A parallel implementation of the conventionally used NDDO (MNDO, AM1, PM3, CLUSTER-Z1) and modified NDDO-WF (CLUSTER-Z2) techniques for semiempirical quantum-chemical calculations on large molecular systems in the sp- and spd-basis, respectively, is described. The atom-pair distribution of data over processors forms the basis of the parallelization. The technological aspects of designing scalable parallel calculations on supercomputers (by using ScaLAPACK and MPI libraries) are discussed. The scaling of individual algorithms and entire package was carried out for model systems with 894, 1920, and 2014 atomic orbitals. The package speedup provided by different multi-processor systems involving a cluster of the Intel PIII processors, Alpha-21264-processor-built machine MBC-1000M, and CRAY-T3E, is analyzed. The effect of computer characteristics on the package performance is discussed.

• J.Kaczmarek, A Method of Integration of Molecular Dynamics and Continuum Mechanics for Solids

  In this paper a formal system called collection of dynamical systems with dimensional reduction is considered. This is a multiscale method of mathematical description which allows to consider molecular dynamics and continuum mechanics within one theoretical framework. Transition between molecular dynamics and continuum mechanics is realized by means of the dimensional reduction procedure. In order to realize such a procedure the formulation of continuum mechanics is modified. This modification consists in incorporation scale of averaging for properties of processes considered during modelling into this formulation. As a result we introduce finite-dimensional fields on continuum only. All fundamental terms of continuum mechanics are now joined with an elementary dynamical system. In such a case continuum mechanics can be obtained by means of the dimensional reduction procedure applied to the elementary dynamical system. A numerical example of vibrating chain of material points is realized in order to show how in practice the dimensional reduction can be carried out. In this example decomposition of processes into slowly and quickly varying parts is accomplished. To this end a finite element representation of averaged fields is applied. Solutions of equations of the elementary dynamical system and the dimensionally reduced dynamical system are compared.

• A.Witkowska, L.Murawski and G.Bergmanski, A Molecular Dynamics Study of the Influence of Chemical Reduction on the Structure of Amorphous Germania

  The contribution is dedicated to the molecular dynamics (MD) study of the structure of reduced germania glass of composition 1Ge 1GeO₂. The work is inspired by a recent report on the formation of Ge clusters in hydrogen reduced germanate glasses containing oxides of heavy metals. The MD simulations have been performed in the microcanonical (NVE) ensemble, using a simple two-body Born-Mayer-Huggins interaction potential. A tendency of germanium atoms to agglomeration into clusters, observed in the present calculations, is compared with an analogous tendency of Bi and Pb atoms, observed previously in the xBi (1-x)GeO₂ and xPb (1-x)GeO₂ systems. The differences in the short and medium-range order in GeO₂ system between the 1Ge 1GeO₂ and GeO₂ glasses are discussed.

• E.Binz and W.Schempp, Digital Information Processing: The Lie Groups defining the Filter Banks of the Compact Disc

  The versality of the compact disc (CD) has quickly become apparent to manufacturers and users alike. Exceeding the expectations of even its most ardent supporters, the CD holographic disc storage system has become one of the most successful consumer electronics products ever introduced. The phenomenal success of the audio CD on the eager worldwide marketplace has encouraged rapid development of CD technology and spawned entirely new high tech applications for the dimpled disc. The Mini Disc (MD), for instance, occupies about one-fourth the area of the standard CD-Digital Audio (CD-DA) format yet provides an identical playing time through efficient data reduction. The essence of digital audio lies in its numerical basis. It is the aim of the present paper to elaborate the mathematical principles underlying the audio CD as far as they are concerned to the format's electronic and holographic principles.

• J.K.Michalczyk and K.Murawski, Numerical Simulations of Air-pollutants in Windy Atmosphere

  Spreading of gaseous pollutants in windy atmosphere is considered by means of numerical simulations of two-dimensional hydrodynamic equations. The parametric studies, which are performed for various magnitudes of a horizontal wind speed, reveal a plume development and a generation of vortices which occur as a result of Kelvin-Helmholtz instabilities. Mass density profiles exhibit high level of spatial and temporal variability. A spectral analysis of these profiles provides variable circular frequency and a wave number.