The first project is devoted to the molecular dynamics simulation of water clusters interacting with the molecules of greenhouse gases (CO2, N2O, CO, and NO), atmospheric gases (O2, Ar and N2) and hydrocarbons (CH4, C2H2 and C2H6). The goal of the project is to investigate dynamic, dielectric and mechanical properties of water cluster systems absorbing admixture molecules and also to calculate the infrared (IR) spectra. Using the method of molecular dynamics we can calculate the wide range of cluster systems properties that we can’t get during physical experiment. Such characteristics as static and frequently dependent dielectric permittivity, the cluster total dipole moment, absorption and reflection coefficients, emitted power of IR radiation, diffusion and compressibility coefficients can be calculated. With the help of Voronoiy polyhedron we can investigate the structure of clusters. Data about thermal, mechanical and concentration stability of water clusters absorbing admixture molecules are obtained.
The main results:
1. The process of clusterization is accompanied by the sharp reduction of the number of scattering centers. The amplification of integral absorption for disperse water systems containing greenhouse gases and hydrocarbons molecules cannot compensate these losses. As a whole, the absorption of greenhouse gases by disperse water system causes the antigreenhouse effect.
2. The absorption of IR radiation by disperse water system is amplified slightly as a result of N2O molecules absorption and it is weakened after CO2 molecules absorption. The easily polarizable acetylene and ethane molecules being in water clusters slightly strengthen the absorption of IR radiation, and methane molecules essentially weaken it. In the case of methane molecules absorption, the window of transparency for IR radiation is observed.
3. Pure water clusters dissipate the energy most slowly. The radiation power is increased after the addition of N2O molecules to water aggregates and it is weakened in the case of CO2 molecules absorption. The addition of CH4 molecules to water clusters strengthens the dissipation rate of the accumulated energy. It grows sharply in the case of C2H2 molecules addition and it is essentially reduced after the adsorption of C2H6 molecules.
4. The absorption coefficient of IR radiation for disperse medium which captured oxygen molecules or atoms decreases, and this value increases for the system that absorbed nitrogen molecules and argon atoms.
The second project is connected with the molecular dynamic simulation of silicon clusters. The goal of the project is the investigation of stability of heating and stretching noncrystalline nanoparticles size from 300 up to 500 atoms, also to research the properties of silicon clusters containing 60 and 73 atoms with different initial atom configurations in vacuum and in hydrogen medium in a wide temperature range. The stability and structure of silicon clusters in dependence of their size is investigated. The distribution of bond length in silicon clusters and average number of bonds per atom for every type of cluster is calculated. The method of noncrystalline silicon clusters stabilization is tested (nanoassembled particle from icosahedron and fullerene, hydrogen putting in and out of fullerene). Data about thermodynamic and kinetic stability of clusters and silicon nanoparticles (containing from 10 up to 500 Si atoms) are obtained. Temperatures and deformation quantity of the beginning of nanoparticles destroying are established.
The main results:
1. Si-glass nanoparticles can be used at high temperatures as the most thermal stable formations. Amorphous silicon nanoparticles are characterized by the higher stability to stretching deformation and their application could be at corresponding conditions.
2. The limit stretching quantity glass and amorphous silicon nanoparticles can have is approximately 4–5%. The kinetic stability criterion is the indicator of melting beginning. In that case the radial direction moving of atoms is dominated over the moving with none zero inclination to nanoparticle radios.
3. At temperatures lower than Debye temperature silicon nanoparticles with the size more than 300 atoms have the stable crystal lattice corresponding to the structure of bulk silicon crystal.
4. Hydrogen environment gives the stabilizing acting to nanoparticles. Nanoassembled particle from icosahedron and fullerene is one of the most stable noncrystalline formation. In a hydrogen medium the temperature interval of "softening” for nanoassembled particle is higher than melting interval for corresponding nanocrystal or amorphous nanoparticle. In a wide temperature range nanoassembled particle keeps the most part of Si-Si bonds.
5. Silicon fullerene isn’t stable formation as its carbon analog can be. The creation of hydrogen "fur coat” outside of fullerene adding to full gives the lowing of probability of atoms evaporation. Effect from hydrogen stabilization is no more than 270–280 K, there is no dramatic decrease of meanings of average number and bond length to these temperatures.
We'v just reseived the results concerning the influence of absorbed water on dielectric properties of silicon dioxide nanoparticle. It is shown in the molecular dynamics simulation that with the use of flexible molecules model the increase of number of water molecules in (SiO2)50cluster up to 40 results in amplification of infrared radiation absorption in a frequency range 0-1000 cm-1. ... Читать дальше »
Clearing the atmosphere from gaseous pollution and aerosols occurs due to the water cycle. As a rule, water in the atmosphere is represented in three aggregation states: gas, liquid and solid. Recently, increased attention is focused on clusters which are formed due to hydrogen bonding. Clusters, especially aggregates of small size, can be considered as a special state of substance. Water vapor as the main representative of water in the atmosphere contributes significantly to its clearing. Clusters are formed from water vapor and subsequently they form water drops or snowflakes which fall as precipitation. At their forming stage and during their subsequent presence in the atmosphere, both clusters and larger formations absorb molecules of pollution substances. ... Читать дальше »