Vārds | Uzvārds | Amats | Tālrunis | Kabinets | E-pasts |

Roberts | Eglītis | Vadošais pētnieks | 26426703 | 437 | Roberts.Eglitis@cfi.lu.lv |

Sergejs | Piskunovs | Vadošais pētnieks | 20093610 | 433 | Sergejs.Piskunovs@cfi.lu.lv |

Jurijs | Mastrikovs | Vadošais pētnieks | 25985004 | 335 | Jurijs.Mastrikovs@cfi.lu.lv |

Dmitrijs | Bočarovs | Vadošais pētnieks | 29622457 m.29622457 | 335 | Dmitrijs.Bocarovs@cfi.lu.lv |

Aleksejs | Gopejenko | Pētnieks | 29558333 | 335 | Aleksejs.Gopejenko@cfi.lu.lv |

Marija | Isupova | Cietvielu fiziķe | Marija.Isupova@cfi.lu.lv | ||

Aleksandrs | Sorokins | Cietvielu fiziķis | Aleksandrs.Sorokins@cfi.lu.lv | ||

Māra | Putniņa | Zinātniskā asistente | Mara.Putnina@cfi.lu.lv | ||

Oļegs | Lisovskis | Zinātniskais asistents | 26130472 | 433 | Olegs.Lisovskis@cfi.lu.lv |

Inta | Isakoviča | Inženiere | Inta.Isakovica@cfi.lu.lv |

Research fields:

- Computer modeling of electronic structures for perfect and defective crystal structures in bulk (3D) and slabs (2D)
- Monoperiodic (1D) and non-periodic (0D) nanomaterials: morphology, electronic structure, and photocatalytic properties
- Development of scattering theory and its practical applications for nanocomposite modeling

**1. ****Computer SIMULATIONS of electronic structures for perfect and defective crystal structures in bulk (3D) and slabs (2D)**

One of our activities is a large-scale electronic structure modeling of various functional materials. Comprehension of this structure allows one to interpret phonon structure, as well as elastic and thermodynamic properties of studying materials. For electronic structure calculations we apply parallel computational methods, which are based on first principles (*ab initio)*, *e.g.*, plane wave (PW) or localized atomic orbitals (LCAO) formalisms, using *VASP* or *CRYSTAL* computer codes, respectively. In order to construct Hamiltonian of crystalline or cluster structure we use density functional theory (DFT) or hybrid approach DFT-HF (partly incorporating Hartree-Fock approximation). During period of 2015-2017 years we have considered a number of solid substances that are important for energetics and material science. Our recent studies include: (*a*) bulk and surface of ternary ABO_{3} oxides (*e.g.*, their solid solutions and interfaces of substrate as support covered by thin film of other perovskite), (*b*) bulk scandium fluoride (ScF_{3}), (*c*) Y_{2}O_{3}- and Y_{2}Ti_{2}O_{7}-enforced steel bulk materials (ODS) used for fusion reactors, (*d*) application of site symmetry formalism for description of point defects in two bulk types of oxides: wurtzite-type ZnO (carbon atom substituted regular oxygen C_{O}) and α-Al_{2}O_{3} (oxygen interstitial O* _{i}* in regular corundum lattice).

*1a. Simulations of perfect and defective perovskites (bulk and surface)*

(a) (b) (c)

*Sketch of the (001) **interface** between two perovskites PbTiO _{3} and SrTiO_{3} (a). Substrate SrTiO_{3} (001) planes are numbered with Arabic numbers. Roman numbers are used to enumerate planes of deposited PbTiO_{3} (001) film. Number zero is used for the central plane of the symmetrically terminated eleven-layer SrTiO_{3} (001) substrate. By means of the B3PW hybrid exchange-correlation functional calculated layer by layer projected density of states of either three UC-thick adsorbate film in PbTiO_{3}/SrTiO_{3} (001) heterostructure (b) or four UC-thick film there (c). Energy scale is plotted regarding the vacuum level. Reference: R.I. Eglitis, S. Piskunov, Yu.F. Zhukovskii, “Ab initio calculations of PbTiO_{3}/SrTiO_{3} (001) heterostructures”. – Phys. Stat. Sol. (c) 13, p. 913–920 (2016).*

As follows from Figs. (b) and (c) containing redox levels *ε*_{O}_{2}/_{H}_{2}_{O} and *ε*_{H+}/_{H2} (red and blue, respectively) inserted inside the DOSs plots, PbTiO_{3}/SrTiO_{3} (001) heterostructures containing even number of atomic PbTiO_{3} (001) nanolayers can be considered as potential candidates for photocatalytic applications, while odd number of PbTiO_{3 }nanolayers cannot since conditions of Eq. *e*_{VB} < *ε*_{HOIL} < *ε*_{O}_{2}_{/H}_{2}_{O} < *ε*_{H+}/_{H}_{2} < *ε*_{LUIL} < *ε*_{CB} are not fulfilled in the latter case (because the top of its valence band *ε*_{VB} overlaps with *ε*_{O}_{2}_{/H}_{2}_{O} level which leads to recombination between electron excited by photon absorption and remaining hole.

*Schematic images for the calculated models of cubic **2×2×2 PbZr _{x}Ti_{1-x}O_{3} (*

*PZT) supercells: a) x = 0, b) x = 0.125, c) x = 0.25, d) x = 0.375, e) x = 0.5, f) x = 0.625, g) x = 0.75, h) x = 0.875, i) x = 1.0. O, Pb, Ti and Zr atoms are shown as small red, large black, middle grey and middle*

*turquoise balls, respectively.*

Lead zirconate titanate Pb(Zr_{x}Ti_{1-x})O_{3} solid solution is considered as one of the most advanced ferroelectric and piezoelectric materials. Consequent variation of Zr (Ti) concentrations significantly affects the atomic and electronic properties of PZT structures. To perform *ab initio* modelling of different morphologies for lead zirconate titanate, we are using approach of hybrid density functional B3PW as implemented in CRYSTAL14 computer code. In this study, we are performing large-scale calculations of such PZT parameters as optimized lattice constants, atomic charges and bond populations, as well as band structure (*e.g.*, band gap) and density of states. *Reference:** A. Gopejenko, S. Piskunov, and Yu.F. Zhukovskii, “Ab initio modelling of the effects of varying Zr (Ti) concentrations on the atomic and electronic properties of stoichiometric PZT solid solutions”. - Comput. Theor. Chem., 2017, 1104, p. 56-60.*

*1b. Simulations on scandium fluoride*

Scandium fluoride (ScF_{3}), having cubic ReO_{3}-type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we have used the results of diffraction and extended X-ray absorption fine-structure (EXAFS) spectroscopy to interpret the influence of NTE on the temperature dependence of infrared absorption spectra of ScF_{3}. Original infrared absorption and EXAFS experiments in a large temperature range are presented and interpreted using *ab initio* lattice dynamics simulations within and beyond quasi-harmonic approximations. *Ab initio* electronic structure calculations based on the linear combination of atomic orbitals method with hybrid functionals are able to reproduce well the experimental values of lattice parameter *a*_{0}, band gap *De _{gap}* and lattice dynamics in ScF

_{3}. However, the simulations performed within quasi-harmonic approximation fail to reproduce the temperature dependence of two infrared active bands due to the bending of F–Sc–F bonds (at 220 cm

^{−1}) and stretching of Sc–F bonds (at 520 cm

^{−1}). This modes are present in the IR absorption spectra. To overcome this problem, an approach beyond the quasi-harmonic approximation is proposed: it accounts for the negative thermal expansion of the lattice and for fluorine atom displacements due to strong F vibrational motion perpendicular to the cubic axes and allows us to explain qualitatively the temperature behavior of infrared spectra of ScF

_{3}.

*Schematic view of ScF _{3} structure with librated ScF_{6} octahedra. The tilt angle Sc–F–Sc is defined as γ . (The small blue balls are fluorine atoms, while the large black balls correspond to scandium atoms.) *

*Reference: S. Piskunov, P.A. Žguns, D. Bocharov, A. Kuzmin, J. Purans, A. Kalinko, R.A. Evarestov, S.E. Ali, and F. Rocca, Interpretation of unexpected behavior of infrared absorption spectra of ScF*_{3}beyond the quasi-harmonic approximation. – Phys. Rev. B, 2016, 93, 214101 (p. 1-9).*1c. Simulations on periodic models of Y _{2}O_{3}- and Y_{2}Ti_{2}O_{7}-enforced steel bulk materials (ODS)*

Application of the ODS steels strengthened by Y_{2}O_{3} precipitates permits growth by 100°C of the operating temperatures for the future fusion and advanced fission reactors. Both size and spatial distribution of oxide particles significantly affect mechanical properties and radiation resistance of ODS steels (*Reference: A. Gopejenko, Yu.F. Zhukovskii, E.A. Kotomin, Yu.A. Mastrikov, P.V. Vladimirov, V.A. Borodin, and A. Möslang, Ab initio modelling of Y–O cluster formation in fсс-Fe lattice. *** – Phys. Stat. Sol. B, 2016, 253, p. 2136-2143)**. Addition of the metallic Ti species (present also as a natural impurity atoms in iron lattice) in the particles of Y

_{2}O

_{3}powder before their mechanical alloying leads to the formation of Y

_{2}Ti

_{2}O

_{7}nanoparticles in ODS steels. In this case the average size of ODS particles reduces to 5 nm being essentially smaller than that of pure Y

_{2}O

_{3}particles (10-20 nm). These results are in the focus of interests in order to study in detail the interaction between two Y and O atoms, two Ti and O atoms as well as between Y, Ti, and O atoms.

(a) (b) (c) (d) (e) (f)

*In (a), (c) and (e) configurations oxygen impurities substitute Fe atoms (O _{Fe}) while in (b), (d) and (e) configurations they are located in empty octahedral sites of fcc-Fe lattice. In all the models, oxygen impurity atoms are located at distance of first nearest neighbors (1NN) from metallic impurity atoms fixed as Ti_{Fe} and Y_{Fe }substitutes*

*1d. Application of site symmetry formalism for description of point defects in two bulk structures of metal oxides*

Carbon-doped ZnO is one of promising materials for technological applications due to its ferromagnetism observed at room temperature. The site symmetry approach applied for C_{O} dopants in ZnO crystal is based on the group-theoretical analysis of the split Wyckoff positions in the perfect crystal supercells with different extensions. Application of supercell model for carbon impurity in O site of wurtzite structured ZnO shows that the calculated formation energy of the point defect essentially depends on the site symmetry of the substituted atom in the supercell.

Arrangement of dopant in less symmetric S1 and S2 symmetry sites of ZnO lattice is found to be essentially more preferable energetically than in essentially more symmetric and traditionally used S6 sites (Eform values in the latter are ~6 times larger). Influence of site symmetry on the electronic structure of C-doped ZnO bulk is well pronounced in the case of large supercell with reduced defect-defect periodic interaction.

*Atop (top) and aside (bottom) views of **a**-Al _{2}O_{3} conventional supercell containing 120 atoms. The distribution of interstitials positions over 4 orbits is shown with different colors: S6 (black), S3 (yellow), S2 (blue), and S1 (grey).*

When using the site symmetry analysis, four possible positions of interstitial oxygen atoms in the a-Al_{2}O_{3} hexagonal structure *S*_{1}, *S*_{2}, *S*_{3} and *S*_{6} have been identified and studied. First principles hybrid functional calculations of the relevant atomic and electronic structures for interstitial O* _{i }*atom insertion in these positions reveal differences in energies of ~1.5 eV. This approach allows us to get the lowest energy configuration corresponding to the lowest

*S*

_{1 }symmetry, avoiding time-consuming calculations. It is shown that the triplet oxygen atom is barrier-less displaced towards the nearest regular oxygen ion, forming a singlet dumbbell (split interstitial) configuration with an energy gain of ~2.5 eV. The charge and spatial structure of the dumbbell is discussed. Our results are important, in particular, for understanding the radiation properties and stability of a-Al

_{2}O

_{3}and other oxide crystals.

*Reference: R.A. Evarestov, A. Platonenko, D. Gryaznov, Yu.F. Zhukovskii, and E.A. Kotomin, First-principles calculations of oxygen interstitials in corundum: a site symmetry approach. – Phys. Chem. Chem. Phys., 2017, 19, p. 25245-25251.***2. ****monoperiodic (1D) and non-periodic (0D) nanomaterials: morphology, electronuc structure and photocatalytic properties**

For effective construction and simulation of properties for carbon, aluminum and boron nitride, titan dioxide, and strontium titanate nanotubes we have used 3D→2D→1D phase transition from bulk to 1D. For equilibrium configurations of single-wall nanotubes, elastic properties, phonon and zone structures have been analyzed. For calculations on equilibrium configurations of double-wall nanotubes, we use parameters corresponding to the maximum of inter-wall interaction energy. For large-scale first principle calculations, we have use only DFT-LCAO method as implemented in *CRYSTAL* code. It is justified mainly in order to avoid the application of 3D models, even in cases when it is necessary to optimize the distance between periodically distributed nanotubes, so the interaction between them could be ignored. Beginning with *CRYSTAL09* code version, special parameter NANOTUBE is used for nanotube construction. (Previously, the linear group formalism was applied for the analysis of 1D nanotubes symmetry, using POLYMER parameter). Arbitrary slab considered as a prototype for nanotube construction can be folded in different ways changing chirality and translation vectors. Chirality vector is placed along the edge of the imaginary slab, which becomes a folding line for nanotube construction. In order to distinguish different nanotubes of same configuration since so-called chirality indices are introduced. Indices determine location and length of chirality vector, and respectively location of translation vector, while these both are perpendicular. Simultaneously, these indices correspond to a number of formula units connected with chirality vector.

During 10 years beginning with 2005 we have published more than 25 papers focused on ab initio simulations of layered CNTs and BN NTs, as well as non-layered AlN, TiO_{2} and SrTiO_{3 }NTs of different chiralities and morphologies. Moreover, we have participated in two EC FP7 projects CATHERINE (2007-2010) and CACOMEL (2011-2014) focused on properties of both perfect and defective CNTs applied mainly in nanoelectronics (** cf. references: 1. Y.N. Shunin, Yu.F. Zhukovskii, N. Burlutskaya, and S. Bellucci, Resistance simulations for junctions of SW and MW carbon nanotubes with various metal substrates. - Centr. Eur. J. Phys., 2011, 9, p. 519-529; 2. Yu.F. Zhukovskii, S. Piskunov, E.A. Kotomin, and S. Bellucci, Simulations on the mechanism of CNT bundle growth upon smooth and nanostructured Ni as well as θ-Al2O3 catalysts. - Centr. Eur. J. Phys., 2011, 9, p. 530-541; 3. Yu.N. Shunin, Yu.F. Zhukovskii, N. Burlutskaya, and S. Bellucci, Theoretical simulations on electric properties of CNT-Me and GNR-Me interconnects using effective media approach. - Procedia Computer Science, 2011, 7, p. 343–345; 4. Yu.F. Zhukovskii, S. Piskunov, and S. Bellucci, Double-wall carbon nanotubes of different morphology: electronic structure simulations. - Nanosci. Nanotechnol. Lett., 2012, 4, p. 1074-1081; 5. Yu.F. Zhukovskii, E.A. Kotomin, S. Piskunov, and S. Bellucci, CNT arrays grown upon catalytic nickel particles as applied in the nanoelectronic devices: Ab initio simulation of growth mechanism. - Proc. NATO ARW „Nanodevices and Nanomaterials for Ecological Security”, Eds. Yuri N. Shunin and Arnold E. Kiv; Springer: Dordrecht, 2012, p. 101-114; 6. J. Kazerovskis, S. Piskunov, Yu.F. Zhukovskii, P.N. D'yachkov, and S. Bellucci, Formation of linear Ni nanochains inside carbon nanotubes: Prediction from density functional theory. - Chem. Phys. Lett., 2013, 577, p. 92-95).** Moreover, we have intensively studied pristine and defective TiO

_{2}and SrTiO

_{3 }NTs potentially enabling for photocatalytic applications (

*1.*

*R.A. Evarestov, A.V. Bandura, M.V. Losev, S. Piskunov, and Yu.F. Zhukovskii, Titania nanotubes modeled from 3- and 6-layered (101 ) anatase sheets: Line group symmetry and comparative ab initio LCAO calculations. – Phys. E, 2010, 43, p. 266-278; 2.***;**

*R.A. Evarestov, Yu.F. Zhukovskii, A.V. Bandura, and S. Piskunov, Symmetry and models of single-walled TiO*_{2}nanotubes with rectangular morphology. - Centr. Eur. J. Phys., 2011, 9, p. 492-501; 3. S. Piskunov and E. Spohr, SrTiO_{3}nanotubes with negative strain energy predicted from first principles. - J. Phys. Chem. Lett., 2011, 2, p. 2566–2570; 4. Yu.F. Zhukovskii, S. Piskunov, J. Begens, J. Kazerovskis, and O. Lisovski, First-principles calculations of point defects in inorganic nanotubes. - Phys. Stat. Sol. B, 2013, 250, p. 793-800

*6. S. Piskunov, O. Lisovski, J. Begens, D. Bocharov, Yu.F. Zhukovskii, M. Wessel, and E. Spohr, C*

*‑*

*, N*

*‑*

*, S*

*‑***Beginning with 2016 year we are involved in H2020 ERA.Net RUS Plus project WATERSPLIT focused on comprehensive simulations of inorganic nanophotocatalysis.**

*, and Fe-doped TiO*_{2}and SrTiO_{3}nanotubes for visible-light-driven photocatalytic water splitting: Prediction from first principles. - J. Phys. Chem. C, 2015, 119, p. 18686−18696).Our current *ab initio* studies on nanostructures performed in the framework of WATERSPLIT project include: (*a*) nanothin films and nanotubes of layered WS_{2} and other transition metal chalcogenides; (b) pristine and doped ZnO nanowires; (c) core-shell wurtzite-structured ZnO NW covered by prismatic nanothin WS_{2} film: d) Fe-Pt 0D nanoclusters. For more accurate description of H_{2}O molecules dissociation upon nanocatalysts immersed in electrolyte accompanying by evolution of hydrogen molecules from electrodes, we have involved simulations of excited states of nanosemiconductors and molecular dynamical simulations.

*2a. Simulations of WS _{2} nanothin 2D films and single-walled 1D nanotubes as prospective nanophotocatalysts*

*Atop (left) and aside (right) views of WS _{2}(0001) nanosheets containing one or two layers as well as transformation of the band gap edges depending on n (center) compared with both the reduction and oxidation potentials (*

*e*

_{H+/H2}and*e*

_{O2/H2O}*, respectively).*

Nanothin films consisting of a few WS_{2} monolayers (MLs) have been experimentally observed to grow upon ZnO nanowires and a-Al_{2}O_{3} substrates. We have found that WS_{2} (0001) nanosheets with thickness between 1 and 10 monolayers to be remarkably suitable for photocatalytic applications in the absence of defects and dopants since their band gaps *D**e** _{gap}* correspond to the range of visible light between the red and violet region (1.5 eV <

*D*

*e*

*< 2.7 eV). Defectfree tungsten disulfide bulk (its*

_{gap}*D*

*e*

*»1.3-1.4 eV found experimentally and 1.58 eV calculated by us) can be considered as the final result of a gradual growth of the number of layers of a pristine WS*

_{gap}_{2}(0001) nanosheet (its

*D*

*e*

*for 1 ML case has been calculated by us 2.53 eV), since the width of*

_{gap}*D*

*e*

*decreases with an increasing nanosheet thickness. For all the WS*

_{gap}_{2}nanosheets considered, the top of the valence band and the bottom of the conduction band (

*e*

_{VB}and

*e*

_{CB}) are properly aligned relative to the oxidation and reduction potentials separated by 1.23 eV, respectively,

*i.e.*,

*e*

_{VB}<

*e*

_{O2/H2O}<

*e*

_{H+/H2}<

*e*

_{CB}. The

*ab initio*calculations reported here have been performed within the formalism of hybrid Density Functional Theory and Hartree-Fock method (using the HSE0 Hamiltonian) properly adapted and carefully verified for atomic, electronic and phonon structure of WS

_{2}bulk and nanosheets. The highest solar energy conversion efficiency (15-18%) usually achieved for

*D*

*e*

*= 2.0-2.2 eV (yellow-green range of visible spectrum) has been found for the 2 ML thick WS*

_{gap}_{2}(0001) nanosheet.

*The electronic structure of gradually growing SW ac- and zz-WS _{2} NTs is simulated depending on d_{NT} increasing from 1.0-1.2 nm up to 5.0-8.8 nm. To estimate diameters of both NTs, we have considered W-containing internal shell. Since thickness of WS_{2} monolayer equals to ~0.3 nm conclusions about dependency of *

*e*

_{gap}*on d*.

_{NT}remain similar*2b. Simulations of pristine and doped wurtzite-structured 1D ZnO [0001]-oriented nanowires considered as prospective nanophotocatalyst*

*Cross-sectional (a) and lateral (b) images of the doped wurtzite-based hexagonal-shaped ZnO NW extended by 6 × 6 atomic shells around the hollow-centred [0001]-oriented axis, containing 216 formula units (or 432=12 × 6 ^{2} atoms) per NW unit cell. The diameter and period of a nanowire are shown by the double arrows d_{NW} (a) and l_{NW} (b), respectively. An example of defect distribution at 3% concentration in a wurtzite-based hexagonal-shaped ZnO NW unit cell is given. Zn and O atoms are shown as small red and middle blue-grey balls, respectively. Outer (yellow) or inner (green) site alternatives are highlighted. The magnitudes of the UC lengths (l_{NW}), the diameters of the nanowires (d_{NW}), as well as the number of atoms per unit cell (n_{NW}) are analyzed in our study. Reference: Yu.F. Zhukovskii, S. Piskunov, O. Lisovski, D. Bocharov, and R.A. Evarestov, Doped 1D nanostructures of transition-metal oxides: first-principles evaluation of photocatalytic suitability (Review). - Isr. J. Chem., 2017, 57, p. 461-476.*

The regular hexagonal prismatic shape of wurtzite-type ZnO nanowires can only be formed if the NW axis is oriented along the [0001] crystallographic direction, being hollow-centred. Arbitrary nanowires can be stabilized when they are terminated by lateral facets, which possess the smallest surface energy among any wurtzite faces. This requirement is fulfilled for the family of six identical and facets of zinc oxide, since they possess the smallest surface energy among wurtzite faces. The last edition of CRYSTAL14 code used for our calculations on ZnO nanowires, contains the new option NANOROD, allowing users to generate differently structured NWs when setting the properly chosen Miller indices of their lateral facets, and thus, simultaneously defining their crystallographic orientations.

*2c. Simulations and experimental verification of core-shell ZnO**/WS2{0001} nanowires*

Core−shell and multi-shell nanowires (NWs) are modern types of axially and radially heterostructured nanomaterials intensively explored during the last decades. Such a complex nanomaterial has several important advantages as compared to conventional two-dimensional (2D) material production technologies: it allows one, for example, to combine materials with lattice mismatch and even to initiate epitaxial growth of shell material on the core template. An epitaxial shell consisting of a WS_{2} nanolayer was grown on ZnO NW core for the first time using the specific procedure. An amorphous layer of WO_{3} was deposited on ZnO NW array and converted into WS2 in S atmosphere at 800 °C. Typical thickness of the WS_{2} shell was found to be 1−5 monolayers. The formation of the WS2 phase was confirmed by TEM studies as well as by Raman scattering and optical spectroscopy.

*(a) Imposition of optimized atomistic model of ZnO*( )*/striped 0.5 ML WS _{2}*( )

*/WS*(0001)

_{2}*interface on top of the TEM image of ZnO/WS*()

_{2 }core−shell NW (scale bar shown in microscopic image is 1 nm) and sections of the same interface across (b)*and (c)*(0001)

*planes. (small red, medium yellow, medium blue, and large green ballscorrespond to O, S, Zn, and W atoms, respectively). The indexing of axes corresponds to ZnO NW.*

**Referenc**e:

*Boris Polyakov, Alexei Kuzmin, Krisjanis Smits, Janis Zideluns, Edgars Butanovs, Jelena Butikova, Sergei Vlassov, Sergei Piskunov, and Yuri F. Zhukovskii,*

*Unexpected epitaxial growth of a few WS*_{2}layers on

*{1-100} facets of ZnO nanowires. - J. Phys. Chem. C 2016, 120, p. 21451−21459**2d. **Fe-Pt 0D nanoclusters*

Bimetallic Fe-Pt nanoparticles with *L1 _{0}* structure are attracting enhanced attention due to their high magnetocrystalline anisotropy and high coercivity what makes them potential material for storage of ultra-high density magnetic data. Fe-Pt nanoclusters are considered also as nanocatalysts for growth of carbon nanotubes of different chiralities. Using the DFT-LCAO CRYSTAL14 code, we perform large-scale spin-polarized calculations on 19 different polyhedral structures of Fe-Pt nanoparticles in order to estimate which icosahedral or

*hcp*-structured morphology is the energetically more preferable. Surface energy calculations of all aforementioned nanoparticles indicate that the global minimum corresponds to the nanocluster possessing the icosahedron “onion-like” structure and Fe

_{43}Pt

_{104}morphology where the outer layer consists of Pt atoms. The presence of the Pt-enriched layer around Fe-Pt core explains high oxidation resistance and environmental stability, both observed experimentally.

*Selected icosahedral (left) and hcp (right) nanocluster models with frozen initial morphology (before geometry optimization). **Referenc**e: A. Platonenko, S. Piskunov, D. Bocharov, Yu.F. Zhukovskii, R.A. Evarestov, and S. Bellucci, First-principles calculations on Fe-Pt nanoclusters of various morphologies. - Sci. Rep., 2017, 7, 10579 (p. 1-8).*

**3. DEVELOPMENT OF SCATTERING THEORY AND ITS PRACTICAL APPLICATION FOR NANOSTRUCTURE MODELING OF NANOCOMPOSITES**

Functionalized carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) nanostructures, serving as the basis for the creation of physical pressure and temperature nanosensors, are considered as tools for ecological monitoring and medical applications. Fragments of nanocarbon inclusions with different morphologies, presenting a disordered system, are regarded as models for nanocomposite materials based on carbon nanoсluster suspension in dielectric polymer environments (e.g., epoxy resins). We have formulated the approach of conductivity calculations for carbon-based polymer nanocomposites using the effective media cluster approach, disordered systems theory and conductivity mechanisms analysis, and obtained the calibration dependences. Providing a proper description of electric responses in nanosensoring systems, we demonstrate the implementation of advanced simulation models suitable for real time control nanosystems. We also consider the prospects and prototypes of the proposed physical nanosensor models providing the comparisons with experimental calibration dependences.

*Two important C-based nanostructures of CNT- and GNR-types have been applied so far: (i) devices with conductive nanoelements for efficient electron transport, electron-impact field transistor (FET-type) switching systems and various functionalized systems with a complex morphology; (ii) nanosensors systems for monitoring of different ecological systems and security aspects. Reference: Stefano Bellucci, Yuri Shunin, Victor Gopeyenko, Tamara Lobanova-Shunina, Nataly Burlutskaya, and Yuri Zhukovskii, Real time polymer nanocomposites-based physical nanosensors: theory and modeling. – Nanotechnology, 2017, 28, 355502 (p. 1-9).*

*FET-type nanodevices as applied in prospective nanosensors: (a) CNT- or GNR-containinig non-perturbed field-impact tranzistor connected with two electrodes (drain and source); (b) physical nanosensors, which conductivity is changed under deformation of CNT or GNR nanoelement; (c) chemical nanosensor, which conductivity can be altered when a sum of free charge on CNT or GNR surfaces changes depending on presence of donor or acceptor molecules in surrounding gas medium.*

The prototypes of nanocomposite pressure and temperature nanosensors have been simulated. The hopping conductivity mechanism gives the adequate description of possible nanosensor qualities. An important problem in manufacturing sensors based on CNTs and GRNs is nanocarbon inclusions orientation, which determines the electrical properties of the future nanosensors. Various morphologies of resistive network models can be realized for evaluation of the total resistance in different nanosensor prototypes.

1. ERA.Net RUS plus project “Computer modeling of nanostructured photocatalyst for efficient hydrogen production from water” (WATERSPLIT) 2015-2018.

2. EUROfusion Enabling Research Project "When and how ODS particles are formed? - X-ray Absorption Spectroscopy and ab initio modelling of ODS steels", (CfP-WP15-ENR-01/UL-01), 2015-2017.

3. EUROFUSION Project - Functional materials (WP-15-PPPT-MAT)

4. Latvian-Ukrainian cooperation program for science and technology (2016-2018) “Novel nanostructured radiation dosimeters based on YAlO_{3}:Mn ceramics: Characterization, modeling and production”

5. National Research program: Multifunctional Materials and composItes, photonics and nanotechnology (IMIS2) (2014 - 2017)

*China:*

- Key Laboratory of Cluster Science of Ministry of Education, Beijing Institute of Technology, Beijing, People's Republic of China (Dr. H. Shi).

*Germany:*

- Duisburg-Essen Universität (Theoretische Chemie), Essen, Germany (Prof. Dr. E. Spohr);
- Institut für Angewandte Materialien (KIT), Karlsruhe, Germany (Prof. Dr. A. Möslang).

*Italy:*

- Laboratori Nazionali di Frascati (INFN), Frascati (Rome), Italy (Dr. S. Bellucci).

*Kazakhstan:*

- L.N. Gumilyov Eurasian National University (Faculty of Physics and Technical Sciencse), Astana, Kazakhstan (Prof. A.T. Akilbekov).

*Russia:*

- Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation (Prof. P.N. Dyachkov);
- St. Petersburg State University (Faculty of Chemistry), Petrodvorets (St. Petersburg), Russian Federation (Prof. R.A. Evarestov).

*Switzerland:*

- Paul Scherrer Institute, Villigen, Switzerland (Dr. M. Krack).

I. **Main papers in International Peer-reviewed Journals ****2015-2017 gados:**

1 R.A. Evarestov, **A. Platonenko**, D. Gryaznov, **Yu.F. Zhukovskii**, and E.A. Kotomin, First-principles calculations of oxygen interstitials in corundum: a site symmetry approach. - *Phys. Chem. Chem. Phys.*, 2017, **19**, p. 25245-25251.

2 **A. Platonenko**, **S. Piskunov**, **D. Bocharov**, **Yu.F. Zhukovskii**, R.A. Evarestov, and S. Bellucci, First-principles calculations on Fe-Pt nanoclusters of various morphologies. - *Sci. Rep.*, 2017, **7**, 10579 (p. 1-8).

3 P. Fu, J. Wang, R. Jia, S. Bibi, **R.I. Eglitis**, and H.-X. Zhang, Theoretical study on hydrogen storage capacity of expanded *h*-BN systems. - *Comput. Mater. Sci.*, 2017, **139**, p. 335-340.

4 M. Sokolov, **R.I. Eglitis**, **S. Piskunov**, and **Yu.F. Zhukovskii**, *Ab initio* hybrid DFT calculations of BaTiO_{3} bulk and BaO-terminated (001) surface *F*-centers. - *Int. J. Mod. Phys. B*, 2017, **31**, 1750251 (p. 1-15).

5 S. Bellucci, **Yu.N. Shunin**, V.I. Gopeyenko, T. Lobanova-Shunina, N. Burlutskaya, and **Yu.F. Zhukovskii**, Real time polymer nanocomposites-based physical nanosensors: theory and modeling. - *Nanotechnology*, 2017, **28**, 355502 (p. 1-9).

6. A.V. Bandura, R.A. Evarestov, S.I. Lukyanov, **S. Piskunov,** and **Yu.F. Zhukovskii**, Simulation of Young's moduli for hexagonal ZnO [0001]-oriented nanowires: first principles and molecular mechanical calculations. - *Mater. Res. Express*, 2017, **4**, 085014 (p. 1-10).

7. D.-C. Yang, R. Jia, Y. Wang, C.-P. Kong, J. Wang, Y. Ma, **R.I. Eglitis**, and H.-X. Zhang, Novel carbon nanotubes rolled from 6,6,12-graphyne: Double Dirac points in 1D material. - *J. Phys. Chem. C*, 2017, **121**, p. 14835-14844.

8. R.A. Evarestov, **S. Piskunov**, and **Yu.F. Zhukovskii**, Site symmetry approach in the supercell model of carbon-doped ZnO bulk. - *Chem. Phys. Lett.*, 2017, **682**, p. 91-95.

9. H. Shi, R. Jia, and **R.I. Eglitis**, First-principles simulations of *H* centers in CaF_{2}. - *Comput. Mater. Sci.*, 2014, **89**, p. 247–256.

10. G. Bonny, A. Bakaev, D. Terentyev, and **Yu.A. Mastrikov**, Interatomic potential to study plastic deformation in tungsten-rhenium alloys. - *J. Appl. Phys.*, 2017, **121**, 165107 (p. 1-13).

11. **A. Gopejenko**, **S. Piskunov**, and **Yu.F. Zhukovskii**, Ab initio modelling of the effects of varying Zr (Ti) concentrations on the atomic and electronic properties of stoichiometric PZT solid solutions. - *Comput. Theor. Chem.*, 2017, **1104**, p. 56-60.

12. **D. Bocharov**, M. Chollet, M. Krack, J. Bertsch, D. Grolimund, M. Martin, A. Kuzmin, J. Purans, and E.A. Kotomin, Analysis of the U *L3*-edge X-ray absorption spectra in UO_{2} using molecular dynamics simulations. - *Progr. Nucl. Energy*, 2017, **94**, p. 187-193.

13. G. Bonny, A. Bakaev, D. Terentyev, and **Yu.A. Mastrikov**, Elastic properties of the sigma W-Re phase: A first principles investigation. - *Scr. Mater.*, 2017, **128**, p. 45–48.

14. **S. Piskunov**, P.A. Žguns, **D. Bocharov**, A. Kuzmin, J. Purans, A. Kalinko, R.A. Evarestov, S.E. Ali, and F. Rocca, Interpretation of unexpected behavior of infrared absorption spectra of ScF_{3} beyond the quasiharmonic approximation.- *Phys. Rev. B*, 2016, **93**, 214101 (p. 1-9).

15.** R.I. Eglitis**, **S. Piskunov**, and **Yu.F. Zhukovskii**, *Ab initio* calculations of PbTiO_{3}/SrTiO_{3} (001) heterostructures. - *Phys. Stat. Sol. C,* 2016, **13**, p. 913–920.

16. **A. Platonenko**, D. Gryaznov, **S. Piskunov**, **Yu.F. Zhukovskii**, and E.A. Kotomin, Charged oxygen interstitials in corundum: first principles simulations. - Phys. Stat. Sol. C, 2016, 13, p. 932–936.

17. **Yu.F. Zhukovskii**, **S. Piskunov**, **O. Lisovski**, E. Spohr, and R.A. Evarestov, Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation. - *Phys. Stat. Sol. B*, 2016, **253**, p. 2120-2128.

18. **A. Gopejenko**, **Yu.F. Zhukovskii**, E.A. Kotomin, **Yu.A.. Mastrikov**, P.V. Vladimirov, V.A. Borodin, and A. Möslang, *Ab initio* modelling of Y–O cluster formation in *fсс*-Fe lattice. - *Phys. Stat. Sol. B*, 2016, **253**, p. 2136-2143.

19. B. Polyakov, A. Kuzmin, K. Smits, J. Zideluns, E. Butanovs, J. Butikova, S. Vlassov, **S. Piskunov**, and **Yu.F. Zhukovskii**, Unexpected epitaxial growth of a few WS2 layers on {11̅00} facets of ZnO nanowires. - *J. Phys. Chem. C*, 2016, 120, p. 21451−21459.

20. **R.I. Eglitis** and **S. Piskunov**, First principles calculations of SrZrO_{3} bulk and ZrO_{2}-terminated (001) surface *F* centers. - *Comput. Cond. Matt.*, 2016, **7**, p. 1-6.

21. **Yu.F. Zhukovskii**, **A. Platonenko**, **S. Piskunov**, and E.A. Kotomin, Ab initio simulations on migration paths of interstitial oxygen in corundum. - *Nucl. Instr. Meth. Phys. Res. B*, 2016, **374**, p. 29–34.

22. **O. Lisovski**, A. Chesnokov, **S. Piskunov**, **D. Bocharov**, **Yu.F. Zhukovskii**, M. Wessel, and E. Spohr, Ab initio calculations of doped TiO_{2} anatase (101) nanotubes for photocatalytical water splitting applications. – *Mater. Sci. Semicond. Process.* 2016, **42**, p. 138-141.

23. **S. Piskunov**, O. Lisovski, J. Begens, **D. Bocharov**, **Yu.F. Zhukovskii**, M. Wessel, and E. Spohr, C‑, N‑, S‑, and Fe-doped TiO_{2} and SrTiO_{3} nanotubes for visible-light-driven photocatalytic water splitting: Prediction from first principles. - *J. Phys. Chem. C,* 2015, **119**, p. 18686−18696.

24. A.V. Bandura, R.A. Evarestov, and **Yu.F. Zhukovskii**, Energetic stability and photocatalytic activity of SrTiO_{3} nanowires: *Ab initio* simulations. - *Royal Soc. Chem. Adv.*, 2015, **5**, p. 24115-24125.

25. P.N. D’yachkov, V.A. Zaluev, **S. Piskunov**, and **Yu.F. Zhukovskii**, Comparative analysis of the electronic structures of mono- and bi-atomic chains of IV, III–V and II–V group elements calculated using the DFT LCAO and LACW methods. - *Royal Soc. Chem. Adv.*, 2015, **5**, p. 91751–91759.

26. P. Fu, R. Jia, C.-P. Kong, **R.I. Eglitis**, and H.-X. Zhang, From determination of the fugacity coefficients to estimation of hydrogen storage capacity: A convenient theoretical method. - *Int. J. Hydrogen Energy*, 2015, **40**, p. 10908-10917.

27. **R.I. Eglitis**, *Ab initio* hybrid DFT calculations of BaTiO_{3}, PbTiO_{3}, SrZrO_{3} and PbZrO_{3} (111) surfaces. - *Appl. Surf. Sci.*, 2015, **358**, p. 556-562.

28. **S. Piskunov** and **R.I. Eglitis**, First principles hybrid DFT calculations of BaTiO_{3}/SrTiO_{3} (001) interface. - *Solid State Ionics*, 2015, **274**, p. 29-33.

29. G.A. Kaptagay, T.M. Inerbaev, **Yu.A. Mastrikov**, E.A. Kotomin, and A.T. Akilbekov, Water interaction with perfect and fluorine-doped Co_{3}O_{4} (100) surface. - Solid State Ionics, 2015, 277, p. *77–82*.

30. **R.I. Eglitis**, Comparative ab initio calculations of SrTiO_{3} and CaTiO_{3} polar (111) surfaces. - *Phys. Stat. Sol. B*, 2015, **252**, p. 635–642.

31. **R.I. Eglitis**, Theoretical prediction of the 5V rechargeable Li ion battery using L_{i2}CoMn_{3}O_{8} as a cathode. - *Phys. Scr.*, 2015, **90**, 094012 (p. 1-4).

32. A. Chesnokov, **O. Lisovski**, **D. Bocharov**, **S. Piskunov**, **Yu.F. Zhukovskii**, M. Wessel, and E. Spohr, Ab initio simulations on N and S co-doped titania nanotubes for photocatalytic applications. - *Phys. Scr.*, 2015, **90**, 094013 (p. 1-7).

33. A. Anspoks, J. Timoshenko, **D. Bocharov**, J. Purans, F. Rocca, A. Sarakovskis, V. Trepakov, A. Dejneka, and M. Itoh, Local structure studies of Ti for SrTi^{16}O_{3} and SrTi^{18}O_{3} by advanced X-ray absorption spectroscopy data analysis. - *Ferroelectrics*, 2015, **485**, p. 42–52.

34.** R.I. Eglitis**, Comparative first-principles calculations of SrTiO_{3}, BaTiO_{3}, PbTiO_{3} and CaTiO_{3} (001), (011) and (111) surfaces. - *Ferroelectrics*, 2015, **483**, p. 53-67.

35. **R.I. Eglitis**, Theoretical modelling of the energy surface (001) and topology of CaZrO_{3} perovskite. - *Ferroelectrics*, 2015, **483**, p. 75-85.

36. **A. Platonenko**, **S. Piskunov**, **Yu.F. Zhukovskii**, and E.A. Kotomin, *Ab initio* simulations on Frenkel pairs of radiation defects in corundum. - *IOP Conf. Ser. Mater. Sci. Eng.*, 2015, **77**, 012001 (pp. 1-5).

**II. Apskati:**

1. **Yu.F. Zhukovskii**, **S. Piskunov**, **O. Lisovski**, **D. Bocharov**, and R.A. Evarestov, Doped 1D nanostructures of transition-metal oxides: first-principles evaluation of photocatalytic suitability (Review). - *Isr. J. Chem.*, 2017, **57**, p. 461-476.

2. **R.I. Eglitis**, *Ab initio* calculations of SrTiO_{3}, BaTiO_{3}, PbTiO_{3}, CaTiO_{3}, SrZrO_{3}, PbZrO_{3} and BaZrO_{3} (001), (011) and (111) surfaces as well as *F* centers, polarons, KTN solid solutions and Nb impurities therein (Review). - *Int. J. Mod. Phys. B*, 2014, **28**, 1430009 (p. 1-43).

**III. Grāmatas un monogrāfiju daļas:**

1. **Yu.F. Zhukovskii**, **S. Piskunov**, **O. Lisovski**, A. Chesnokov, and **D. Bocharov**, First principle evaluation of photocatalytic suitability for TiO2-based nanotubes. - Chapter in a book: W. Cao (Ed.) Semiconductor Photocatalysis - Materials, Mechanisms and Applications (InTech Open Access Publishers, Croatia), 2016, p. 105-133.

2.** Yu.F. Zhukovskii**, Boron and Metal Diborides. – *Chapter 4 in book:* *R.A. Evarestov, Theoretical Modeling of Inorganic Nanostructures* (Springer-Verlag, Berlin, Heidelberg) 2015, p. 217-251.

3. **Yu.F. Zhukovskii**, Group IV Semiconductors. – *Chapter 5 in book:* *R.A. Evarestov, Theoretical Modeling of Inorganic Nanostructures* (Springer-Verlag, Berlin, Heidelberg) 2015, p. 253-346.

4. **Yu.F. Zhukovskii**, Nitrides of Boron and Group III Metals. – *Chapter 6 in book: R.A. Evarestov, Theoretical Modeling of Inorganic Nanostructures* (Springer-Verlag, Berlin, Heidelberg) 2015, p. 347-427.

5. **Yu.N. Shunin**, Spintronic Nanomemory and Nanosensor Devices (Lambert Academic Publishing, Saarbrücken), 2015, p. 2-49.

6. *Proceedings of NATO Advanced Research Workshop "Nanodevices and Nanomaterials for Ecological Security"*. NATO Science for Peace, Series B - Physics and Biophysics (Eds. **Yu.N. Shunin** and A.E. Kiv, Springer: Dordrecht), 2012, 363 p.

7. **Yu.F. Zhukovskii**, **D. Bocharov**, D. Gryaznov, and E.A. Kotomin, First Principles Simulations on Surface Properties and Oxidation of Nitride Nuclear Fuels. – *Chapter 5 in book: Advances in Nuclear Fuel* (Ed. Sh.T. Revankar, InTech Open Access Publishers), 2012, p. 95-122.