Laboratory of electron-nuclear and molecular processes

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    Laboratory of electron-nuclear and molecular processes

    The Laboratory of electron-nuclear and molecular processes (LENMP) was organized in 2008. It's Head is Sc.D. Evegeny Tkalya.

    The Laboratory is specilized in a wide range of theoretical studies at the junction of atomic and nuclear physics, nuclear spectroscopy and solid state physics. A number of recent publications is devoted to the quantum-mechanical approach to the solution of nanotechnological problems. The Laboratory works in close collaboration with several experimental groups at SINP and RAS institutes.

    The basic directions of scietific research are the following:
    A) Nuclear spectroscopy and related fields
    - theoretical studeis of the processes of interaction between the nucleus and the atomic shell for different orders of perturbation approach of quantum electrodynamics;
    - processes of excitement and decay of isomeric levels of atomic nuclei in high-temperature dense plasma;
    - influence of the medium on the properties of nuclear transitions of low and super-low energy;
    - bremsstrahlung radiation at alfa-decay of the nuclei.

    B) Solid state physics and atomic physics
    - influence of physics-chemical environment on beta-decay of nuclei;
    - electronic properties of rare earth metals and their compositions.

    C) Calculation and theoretical studies of nanostructures
    - development of a software complex (package) for calculations of the properties of the materials and nanostructures basing on the quantum-mechanical laws at atomic-molecular level with series transition to macroscopic level by means of statistical physics and thermodynamics;
    - development of quantitative numerical models in order to describe and predict the properties of the matter at different spatial and temporal scales.

    The following studies are accomplished in the Laboratory over recent years:
    1. Inadequacy of the concept of isomeric hafnium bomb is proved.
    2. A scheme of nuclear laser of optic range is supposed and a possibility for the development of such device at the transiton with energy of 7.6 eV in the nucleus 229Th is explained theoretically. Decay channels of low-laying isomere 229mTh (3/2+, 7.6 eV) are predicted: "nuclear light" in dielectric; conversion on conductivity electrons in metal; electronic bridge in atom; alfa-decay.
    3. A theory of the processes of excitement and decay of nuclear levels at the transitions of the electrons in the atomic shell, including those with taling into consideration dynamical effect of the nucleus volume.
    4. Excitiment of the nuclei of 181 Ta in laser plasma was found during a cycle of studies on mechanisms of excitement of atomic nuclei isometic levels in high-temperature dense laser plasma.
    5. Bremsstrahlung spectra accompanying alfa-decay were predicted.
    6. Probability of spontaneous radiation of certain multipolarity in the medium are expressed as funcltions of ε and μ.
    7. Acceleration of the decay (K-entrapment) of the nucleus 7Be inside the fullerence C60 is exlained as a result of production of attraction potential and wave function with a node. Lifetime of 7Be inside (a complex of 7Be@C36) and outside (a molecule 7Be-C36) of the fullerene C36 is predicted.
    8. A new class of materials - materials for storage of hydrogen - basing on carbon rings are discovered: a) aromatic hydrocarbon doped with Boron and stabilized with Lithium, Potassium or Magnesium; b) Boron-Carbon nanotubes stabilized with Lithium.
    9. Excitement spectrum of the states of fullerene С60 molecule is studied on an approximation of configuration interaction with basis consisted of twice excited determinates.
    10. Electronic structure of Cerium (Ce2) dimer and its influence on the phase transitions in the crystallic state of Cerium are studied.

    A number of projects in the field of solid state physics and nanotechnolocies is based on software developed in the Laboratory. Review of some codes is presented below.

    MuScalT – software complex for the calculations of microsystems (up to 100 atoms) properties basing on fundamental laws of quantum mechanics (so-called ab-initio calculations). Due to the recent numeric methods and effective programming, AlgoQMT is remarkably advantageous in the ratio of running speed and accuracy of calculations in comparison with all other analogous. In fact, calculation of such level provides accuracy as the best experimental methods and at the same time allows to study an effect more flexible and to vary parameters within the significantly wider range due to no need of material realization of a system.

    MuScalRHF - software for the calculations of microsystem (up to 100 atoms) energy by method Hartree-Fock taking into account electron-electron correltaions by method of Meller-Plesset (MP2). The software allows to use a method of resolution of the identity (or RI-method) in order to achieve essential acceleration of calculations of electron-electron integrals. Due to this method it is possible to reduce a numbe of integrals' calculations from standard N4 to the order of N3, where N - a number of basis fucntions for calculation. Value N can be up to several thousands, and the program needs 2-3 orders of magnitude less memory and processor time, than standard method. It allows to calculate the systems of several dozens of atoms with accuracy of the tenth kcal/mol at laptop. Other methods such as the method of density functional or semi-empiric methods can't provide such level of accuracy for inter-molecular interaction. The program also provides calculations of dipole and quadrupole moments of the molecule, electronic density and some other features of the system.

    MuScalOpt - software for optimization of the molecular system geometry which is operated both in the presence of analytical gradients of system's energy, and in their absence or insuffient accuracy. Two optimization modes are available:
    - optimization of intermolecular geometry of "hard" molecules;
    - full optimization of the system (intramolecular and intermolecular).
    Format of molecule's parametrization allows also to "freeze" separate degrees of freedom of the system, to apply simmetry restrictions. Besides, the program can calculate harmonic and anharonic frequencies of molecule's oscillations and to provide information aboout vibration modes of the system for its further visualization.

    MuScalPlot - software for calculation of electronic density and providing data for its visualization allows to obtain electronic density of the system in general and molecular orbitals separately. It allows to make chemical anaysis of molecular systems, to explain and predict their properties.

    MuScalCI - software for calculations of electron-electron correlations of microsystmes (up to 100 atoms) of hegher, than MP2 level, and to obtain electronic spectra of molecules.

    The results of the studies of the Laboratiry scientists are published in the leading international and Russian journals: Physical Review A, B, C, Physical Review Letters, Nuclear Physics A, The Journal of Physical Chemistry C, Advances in Physical Sciences (Physics - Uspekhi), Journal of Exlperimental and Theoretical Physics, Letters to the Journal of Experimental and Theoretical Physics, etc.