arXiv subjects

A. I. Podlivaev

Publications and source records attributed to A. I. Podlivaev.

27 records · Page 2Linked to original sources

arXiv2006

Formation of a "Cluster Molecule" (C20)2 and its thermal stability

The possible formation of a "cluster molecule" (C20)2 from two single C20 fullerenes is studied by the tight-binding method. Several (C20)2 isomers in which C20 fullerenes are bound by strong covalent forces and retain their identity are found; actually, these C20 fullerenes play the role of "atoms" in the "cluster molecule". The so-called open-[2+2] isomer has a minimum energy. Its formation path and thermal stability at T = 2000 - 4000 K are analyzed in detail. This isomer loses its molecular structure due to either the decay of one of C20 fullerenes or the coalescence of two C20 fullerenes into a C40 cluster. The energy barriers for the metastable open-[2+2] configuration are calculated to be U = 2 - 5 eV.

cond-mat.mes-hall↗

arXiv2006

Decay and fusion as two different mechanisms of stability loss for the (C_20)_2 cluster dimer

The thermal stability of the (C_20)_2 cluster dimer consisting of two C_20 fullerenes is examined using a tight-binding approach. Molecular dynamics simulations of the (C_20)_2 dimer at temperatures T = 2000 - 3500 K show that the finite lifetime τof this metastable system is determined by two fundamentally different processes, the decay of one of the C_20 fullerenes and the fusion of two C_20 fullerenes into the C_40 cluster. The activation energies for these processes Ea = 3.4 and 2.7 eV, respectively, as well as their frequency factors, have been determined by analyzing the dependence of τon T.

cond-mat.mes-hall↗

arXiv2006

Numerical simulation of the thermal fragmentation process in fullerene C60

The processes of defect formation and annealing in fullerene C60 at T=(4000-6000)K are studied by the molecular dynamics technique with a tight-binding potential. The cluster lifetime until fragmentation due to the loss of a C2 dimer has been calculated as a function of temperature. The activation energy and the frequency factor in the Arrhenius equation for the fragmentation rate have been found to be Ea = (9.2 +- 0.4) eV and A = (8 +- 1)10^{19} 1/s. It is shown that fragmentation can occur after the C60 cluster loses its spherical shape. This fact must be taken into account in theoretical calculations of Ea.

cond-mat.mes-hall↗

arXiv2005

Stone-Wales Transformation Paths in Fullerene C60

The mechanisms of formation of a metastable defect isomer of fullerene C60 due to the Stone-Wales transformation are theoretically studied. It is demonstrated that the paths of the "dynamic" Stone-Wales transformation at a high sufficient for overcoming potential barriers) temperature can differ from the two "adiabatic" transformation paths discussed in the literature. This behavior is due to the presence of a great near-flat segment of the potential-energy surface in the neighborhood of metastable states. Besides, the sequence of rupture and formation of interatomic bonds is other than that in the case of the adiabatictransformation.

cond-mat.other↗

arXiv2005

Anomalous Thermal Stability of Metastable C_20 Fullerene

The results of computer simulation of the dynamics of fullerene C_20 at different temperatures are presented. It is shown that, although it is metastable, this isomer is very stable with respect to the transition to a lower energy configuration and retains its chemical structure under heating to very high temperatures, T ~ 3000 K. Its decay activation energy is found to be E_a ~ 7 eV. Possible decay channels are studied, and the height of the minimum potential barrier to decay is determined to be U = 5.0 eV. The results obtained make it possible to understand the reasons for the anomalous stability of fullerene C_20 under normal conditions.

cond-mat.mes-hall↗

arXiv2004

On the momentum-space approach to calculation of one-electron energy spectra and wave functions of atomic clusters

Momentum-space approach to calculation of one-electron energies and wave functions proposed initially by Fock for a hydrogen atom and considered later by Shibuya, Wulfman, and Koga for diatomic molecules is applied to clusters composed of three and more atoms. The corresponding basis set in the coordinate space is of the Sturmian type since all the hydrogenlike orbitals in this set have a common exponent, i.e., correspond to the same energy (as opposed to one-electron atomic orbitals). By the examples of He$_4^{+7}$ and He$_6^{+11}$ cluster ions it is shown that increase in the number of orbitals in the set results in rapid convergence of eigenenergies and eigenfunctions of highly excited states. The momentum-space approach to the one-electron many-center problem may be used for various solid-state and quantum-chemical applications.

quant-ph↗

arXiv2002

Metastable quasi-one-dimensional ensembles of nitrogen clusters N_8

By means of ab initio and tight-binding calculations it is shown that metastable nitrogen clusters N_8 (boats) can form quasi-one-dimensional ensembles in which the nearest clusters N_8 are bound to each other by covalent bonds. Those ensembles are characterized by rather high energy barriers (~ 0.3 eV) that prevent the fission of the ensembles into isolated N_8 clusters and/or N_2 molecules.

cond-mat.mes-hall↗

arXiv2001

Metastability of the Three-Dimensional Carbon Cluster Prismane C$_8$

Stability of recently predicted cage-like carbon cluster C$_8$ (prismane) against its transformations to structures lying at lower energies is studied theoretically. The smallest energy barrier inhibiting prismane transformation is shown to be 0.44 eV, in qualitative agreement with the value of activation energy for prismane decay calculated by molecular dynamics simulations. A rather high value of the barrier suggests the possibility of experimental observation of this cluster at ambient pressure.

physics.atm-clus↗

arXiv1995

Supercurrent States in 1D Finite-Size Rings

We consider topological supercurrent excitations (SC) in 1D mesoscopic rings. Under certain conditions such excitations are well-defined except for (i) a tunneling between resonating states with clockwise and anti-clockwise currents, which may be characterized by the amplitude $Δ$, and (ii) a decay of SC assisted by phonons of the substrate, both effects being macroscopically small. Most attention is paid to the calculation of the macroscopic scaling of $Δ$ (the main superfluid characteristic of a mesoscopic system) under different conditions: a commensurate system, a system with single impurity, and a disordered system. The results are in a very good agreement with the exact-diagonalization spectra of the boson Hubbard models. Apart from really 1D electron wires we discuss two other important experimental systems: the 2D electron gas in the FQHE state and quasi-1D superconducting rings. We suggest some experimental setups for studying SC, e.g., via persistent current measurements, resonant electro-magnetic absorption or echo signals, and relaxation of the metastable current states.

cond-mat↗