Research area: Lattice Dynamics, phonons and other quasi-particle excitations in solids:

• Propagation and localization of vibrations in ill-ordered crystals, heterogeneous structures and disordered systems
• Vibrational characteristics of crystals with complex defects;
• Dynamics of complex crystal lattices, strongly anisotropic crystal structures, and quasi-low-dimensional lattices.
• Quasi-particle spectra of nanosystems.

Main 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. (with E.S. Syrkin and A.M. Kosevich)
• Localization and propagation of vibrations in heterogeneous crystals and disordered solid solutions
• Creation of calculation models for investigation of electron and phonon spectra of graphite and carbonic thin films.

Main Publications:

1. 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.
2. 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.
3. 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, 2001.
4. 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.
5. S.B. Feodosyev, I.A. Gospodarev, M.A. Strzhemechny, R.J. Hemley, Phonon Assisted Ortho- Para Conversion in Solid H₂ Under Pressure, PHYSICA B: Physics of Condensed Matter, 300, 186, 2001.
6. 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, 2000.
7. E.T. Verkhovtseva, I.A. Gospodarev, A.V. 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, 2003.
8. A.V. Kotlyar and S.B. Feodosyev, Local oscillations in crystal lattices with a simply connected region of the quasi-continuonsphonon spectrum , Low Temperature Physics, 32, No 3, 256, 2006.
9. I.A. Gospodarev, V.I. Grishaev, O.V. Kotlyar, K.V. Kravchenko, E.V. Manzhelii, E.S. Syrkin, and S.B. Feodosyev, Ioffe–Regel crossover and boson peaks in disordered solid solutions and similar peculiarities in heterogeneous crystal structures Low Temperature Physics, 34, No 8, 655, 2008.
10. E.S. Syrkin, S.B. Feodos’ev, K.V. Kravchenko, A.V. Eremenko, B.Ya. Kantor and Yu.A. Kosevich, Flexural rigidity of layers and its manifestation in the vibrational characteristics of strongly anisotropic layered crystals. Characteristic frequencies and stability conditions in quasi-two-dimensional systems, Low Temp. Phys. 35, No 2 158, 2009.
11. I.A. Gospodarev, K.V. Kravchenko, E.S. Syrkin and S.B. Feodos’ev Quasi-two-dimensional features in the phonon spectrum of graphite Low Temp. Phys. 35, No 7 589, 2009.
12. A. Feher, I.A. Gospodarev, V.I. Grishaev, K.V. Kravchenko, E.V. Manzheliĭ, E.S. Syrkin and S.B. Feodos’ev, Effect of defects on the quasiparticle spectra of graphite and graphene, Low Temp. Phys. 35, No 8, 679, 2009
13. I.K. Galetich, I.A. Gospodarev, V.I. Grishaev, A.V. Eremenko, K.V. Kravchenko, , V.A. Sirenko, S.B. Feodosyev, Vibrational characteristics of the niobium dichalcogenide. Bulk samples and nanofilms, Superlattices and Microstructures, 45, No 6, 564, 2009
14. I.A. Gospodarev, V.V. Eremenko, K.V. Kravchenko, V.A. Sirenko, E.S. Syrkin and S.B. Feodos’ev Vibrational characteristics of niobium diselenide and graphite nanofilms Low Temp. Phys. 36, No 4, 344 2010.
15. Alexander Feher, Eugen Syrkin, Sergey Feodosyev, Igor Gospodarev and Kirill Kravchenko Quasi-Particle Spectra on Substrate and Embedded Graphene Monolayers, in: “Physics and Application of Graphene – Theo-ry” (ed. S. Mikhailov) “InTex” Open Access Publisher, ISBN 978-953-307-996-7 Croatia, 2010
16. A Feher, E. Syrkin, I. Gospodarev, E. Manzhelii, A. Kotlyar, K. Kravchenko, The Features of Low Frequency Atomic Vibrations and Propaga-tion of Acoustic Waves in Hete-rogeneous Systems, in: “Waves in Fluids and Solids” (ed. R.P. Vila) “InTex” Open Access Publisher, ISBN 978-953-307-246-3 Croatia, 2011.
17. I. Gospodarev, O.V. Kotlyar, K.V Kravchenko, E.V. Manzhelii, E.S Syrkin, A.V.Yeremenko, I.K. Galetich, Low Temperature Peculiarities of Quasi-Particle Spectra of Disordered Solid Solutions, in: “Contemporary Problems of Mathematics, Mechanics and Computer Sciences” (eds. N.N. Kizilova, G.N. Zholtkevich) PRB Virovec’,ISBN 978-966-2579-92-5 Ukraine, 2011
18. A.Feher, I.Gospodarev, O.Kotlyar, K.Kravchenko, E.Manzhelii, E.Syrkin, S.Feodosyev Impurity levels in the electron spectra of graphene, Superlattices and Microstructures, 53, 55, 2013
19. I.A. Gospodarev, A.V. Eremenko, K.V. Kravchenko, A.F. Sirenko, V.A. Sirenko, E. S. Syrkin, S.B. Feodosyev, and Yu. A. Shabakaeva, Distinctive Features of Thermal Expansion of Niobium Diselenide, Physics of the Solid State,. 55 No. 4, 825, 2013