Sergey (Sergiy) Feodosyev, Senior Researcher.

E-mail: feodosyev@ilt.kharkov.ua

Graduated from Kharkov State University in 1975.

PhD Phys & Math, ILTPE, 1985.

Started work at ILTPE in 1975.

Research area: Lattice Dynamics:

• Propagation and localization of oscillations in slightly ordered crystals;

• Oscillatory characteristics of crystals with complex defects; 

• Dynamics of complex crystal lattices and strongly anisotropic crystal structures.

Achievements:

• The main distinctive peculiarities of phonon spectra of strongly anisotropic layered and chain crystals were determined and systemized (with E.S. Syrkin); the effect of these peculiarities on the behaviour of oscillatory thermodynamics characteristics of this kind of compositions was studied, in particular, there was defined a microscopic theory of the so-called "membrane effect".

• Propagation and localisation characteristics of oscillations in lattices of various dimensions were studied and a new method for the localized states description based on J-matrix was suggested.

• A number of microscopic calculations on the atomic dynamics of the definite crystal structures both perfect and defected were made.

• Phonon spectra behaviour of crystals with the weakened effect of crystal atoms ordering regularity (systems with complex defects, multi-layered structures of HTSC-type, nanoclusters, etc.) was investigated on microscopic level; it was found that the oscillatory characteristics of such compositions were definitely conditioned by its strong spatial nonhomogeneity as well as the local anisotropy of interatomic interaction. (See: Syrkin and Kosevich) 

Main Publications:

1. E.S. Syrkin, S.B. Feodosyev, Contribution of Optical Vibrations to the Low-Temperature Specific Heat of Layered Crystals, FNT, 8, 381, 1982.

2. S.B.Feodosyev, E.S.Syrkin, Influence of Noncentral Interatomic Forces on the Low Temperature Thermodynamics of Layered Crystals, FNT, 9, 528, 1983.

3. S.B.Feodosyev, I.A.Gospodarev, E.S.Syrkin, Anomalies of Linear Expansion Coefficient in Highly Anisotropic Crystals at Low Temperature, Phys, Stat. Sol (b), 150, K19, 1988. 

4. S.B.Feodosyev, M.A.Mamalui, E.S.Syrkin, Dynamical Characteristics of Infinite and Semi-Infinite 1D Structure with Defects in Presence of Activation, Synthetic Metals, 121, 1333-1334, 2001. 

5. I.A. Gospodarev, A.V. Grishaev, E.S. Syrkin, S.B. Feodosyev, Local Vibrations of FCC-Crystals with Two Parametric Substitution Impurities, Phys. Solid State, 42, N12, 2000.

6. S.B. Feodosyev, I.A. Gospodarev, M.A. Strzhemechny, R.J. Hemley, PhononЦAssisted Ortho- Para Conversion in Solid H₂ Under Pressure, PHYSICA B: Physics of Condensed Matter, 300, 186-197, 2001.

7. S.B. Feodosyev, I.A. Gospodarev, A.M. Kosevich, E.S. Syrkin, Quasi-Low-Dimensional Effects in Vibrational Characteristics of 3D-Crystals, Phys. Low Dim. Str., 10/11, 209, 1995.

8. A.M. Kosevich, A. Mayer, S.B. Feodosyev, I.A. Gospodarev, V.I. Grishaev, E.S. Syrkin, Atom Dynamics of Micro-Clusters on Atomically Smooth Surfaces, Superlattices and Microstructures, 27, No1, 7-14, 2000.

9. E.T. Verkhovtseva, I.A. Gospodarev, V.I. Grishaev, S.I. Kovalenko, D.D. Solnyshkin, E.S. Syrkin, S.B. Feodosyev, Atom Dynamics and the Problem of the Structural Stability of Free Clusters of Solidified Inert Gases, Low Temperature Physics, 29, No 5, 386-393, 2003.