The prerequisites for the mass use of hygrothermal probes as an affordable and effective tool for remote operational control of grain quality preservation of grain quality during its storage are considered as an alternative to the use of classical thermo probe, which are still widely used to monitor the state and identify centers of self-heating of grain stored in floor storage warehouses. Hygrothermal probe, with their budgetary availability, provide increased sensitivity in comparison with thermo probe and allow detecting self- heating of grain at its initial stages.

Differential scanning calorimetry has been used to carry out a precision study of KNO3 introduced into a silicate nanoporous matrix. Heat capacity peaks associated with ferroelectric phase transitions were found and examined. The characteristics of these transitions were examined in terms of the theory of diffuse phase transitions. A hypothesis was made that there exists a minimum size of pores in the nanocomposite at which KNO3 is in the fully ferroelectric state at room temperature.

A complex of technical solutions is presented which makes it possible to study the influence of external factors on changes in the indicator of fat acidity value (FAV) and a range of other parameters characterizing the quality of preservation of long-term stored wheat grains in South Russia. Storage conditions (natural climatic, model) and also the effect of dust suppression treatment of grain by oil glazing that is carried out in some grain terminals in the South of Russia were taken as controlled external factors. New data has been obtained on changes in parameters of food suitability of the wheat grains during storage under model conditions with varying degrees of severity of climatic conditions in South Russia. After 6 months of storage the most considerable changes in FAV value were found for 4th class of wheat stored in natural climatic conditions with intensive insolation, the increase was 1.7 mg KOH/1 g of fat (from 7.3 mg KOH/1 g of fat up to 9.0 mg KOH/ 1g of fat). Minimum changes in the same parameter for the same storage period were observed for the wheat of the 3rd class stored in a thermostat at a stable high temperature of 35 ºС (from 11.6 mg KOH/1 g of fat to 11.5 mg KOH/1 g of fat). For wheat of the 4th class, the changes were 0.7 mg KOH/1 g of fat (from 7.8 mg KOH/1 g fat to 8.5 mg KOH/1 g of fat). Analyzes of stored wheat grains subjected to dust suppression by the oil glazing showed similar results, which allows us to state the absence of a significant effect of oil glazing on changes in wheat properties during its storage.Based on the results of the experimental analysis and a generalization of the data obtained an assumption was made on the possible reasons for the lack of pronounced trends in the data for the expected increase of FAV value in food suitability of the wheat grain when it is stored under typical model conditions of South Russia. The likely reason for this is the corresponding moisture state of grain, the water activity of grain was about 0.45. Such a low value was due, in particular, to the fact that samples of model-stored grain had a limited volume and do not reproduce the mass transfer processes that involve deep layers of the grain mass (because of the mass absence), which takes place during storage of grain in an industrial environment. The tools were proposed for the operational monitoring of the moisture state of wheat grain during storage. Moreover, a plan has been developed to expand the field of modelling storage processes in terms of varying the moisture state of the stored wheat grain samples with an assessment of the influence of moisture state on the dynamics of changes in the parameters to be controlled.

Raman spectra of Hg2Br2 model improper ferroelastic crystals have been investigated in a wide range of high hydrostatic pressures. Baric dependences of the phonon frequencies have been obtained; of greatest interest are the observed soft mode originating from the slowest TA1 acoustic branch at the Brillouin zone boundary (X point) of the tetragonal phase and the anomalous behavior of this mode. In the ferroelastic phase spectra, the ignition of the second acoustic TA2 from the same point has also been detected and its baric behavior has been studied. Under sufficiently high pressures, splitting of doubly degenerate phonons with the Eg symmetry has been observed and explained. The parameters of the Grüneisen constants have been determined from the baric dependences of the phonon frequencies and discussed.

The structure of the Hg2F2 compound was studied experimentally and theoretically within the density functional theory. X-ray diffraction studies enabled us to determine the space group of the crystal (I4/mmm), and the comparison of the experimentally obtained Raman spectra of these crystals with the theoretical ones enabled us to find and uniquely identify all bands in the spectra. The stability of the I4/mmm phase was analyzed in a wide range of uniaxial and hydrostatic pressures. It is shown that the uniaxial compression of a crystal along a tetrad axis results in a phase transition to the Cmcm structure at Pc = 8 GPa, whereas the hydrostatic compression results in a previously unknown phase transition to the Cmca phase at Pc = 9 GPa. The calculations of the cubic nonlinear susceptibility of Hg2F2 predict a giant value of this quantity.

Raman spectra of model improper ferroelastics (Hg2Br2 crystals) have been analyzed in a wide range of hydrostatic pressures. The baric dependences of the phonon frequencies are obtained. The revealing and anomalous behavior of the soft mode, which is genetically related to the acoustic phonon (ТА1) at the Brillouin zone boundary (point X) of the tetragonal phase, are most interesting. The buildup of the second acoustic phonon (ТА2) from the same point has also been found in the ferroelastic-phase spectra, and its baric behavior has been investigated. The splitting of doubly degenerate phonons of the Eg symmetry has been revealed at fairly high pressures and explained.

Monocrystals of lanthanum hexaboride LaB6 containing both natural boron and its isotopes 10B and 11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.

Thermal effects in some nanoporous silicate matrices (with different pore sizes) loaded with ferroelectric NaNO 2 from both a saturated solution and from a melt have been studied in a wide temperature range including the phase transition temperatures. All the samples reliably demonstrate maxima of the heat capacity, corresponding to first-order ferroelectric phase transitions. The characteristics of the maxima (intensity, half-width, phase transition temperature, etc.) have been determined. A more complex situation is the observation of an incommensurable phase (sinusoidal antiferroelectric), in particular, in the case of pore sizes comparable to the period of an “incommensurable” wave, the manifestation of which can be explained by the appearance of a corresponding orientation of sodium nitrite nanocrystals in pores of these matrices. It is found that the characteristics of above noted effects depend on the prehistory of the samples under study.

A theoretical model based on long-range dispersion corrections of the charge density functional is proposed for model Hg2Cl2 calomel crystals, typical representatives of molecular inorganic compounds where the intermolecular interaction is found to play an important role. This model successfully describes the electronic state and the phonon spectrum of the above crystal, predicts the earlier unstudied phase transition at high hydrostatic pressure. Study of the baric behavior of the phonon spectrum with Raman spectroscopy observes the soft mode in the low-symmetry orthorhombic phase with the frequency softening as the pressure rises. Pressures above 9 GPa considerably transform the Raman spectra, indicating a structural phase transition.

N-benzylanyline single crystals are grown, and X-ray diffraction probing of their structure allows their symmetry to be attributed to the C 2h. 5 phase. Polarized Raman studies of these crystals allow the frequencies of lattice phonons to be estimated and their symmetry to be established. The abnormal behavior of the two lowest-frequency Ag symmetry soft modes, the condensation of which is not detected below the melting point (36–38°C), is noted. The possibility of a high-temperature virtual phase transition and praphase is discussed. Theory group consideration of the praphase allows determination of its symmetry and the symmetry of phonons related to the virtual phase transition.

Differential scanning calorimetry has been used to carry out a high-precision study of sodium nitrite NaNO2 incorporated into different silicate nanoporous matrices. Heat-capacity maxima due to smeared ferroelectric phase transitions have been discovered. Characteristics (intensity, half-width, phase-transition temperature, etc.) of the maxima have been investigated. Heat-capacity maxima related to an incommensurable phase transition have been reliably identified. The maxima can be attributed to the formation of appropriate orientation of sodium-nitrite nanocrystals in matrix pores.

The influence of empirical dispersion corrections of the density functional has been investigated when calculating the electronic structure of molecular crystals undergoing structural phase transitions. A phonon spectrum of calomel and benzyl crystals has been calculated, dispersion dependences of optical and acoustic phonons have been constructed, and the phase transition model in calomel crystals has been studied.

Raman spectra of incipient ferroelastics, namely, Hg 2 I 2 crystals, have been investigated over a wide range of hydrostatic pressures. Linear pressure dependences of phonon frequencies have been obtained at P < P c ). It has been found that jumps and breaks are observed in these dependences at the phase transition point P c = 9 kbar. The Grüneisen parameters of the Hg 2 I 2 crystals have been determined and discussed. The Raman spectra of the ferroelastic phase ( P > P c ) in different polarizations exhibit excitation of acoustic vibrations from the X point of the Brillouin zone boundary, including transverse acoustic (TA 1 and TA 2 ) and longitudinal acoustic (LA) phonons. The Raman spectra of the ferroelastic phase have been interpreted based on the analysis of the experimental results, and a model of the phase transition in these crystals has been proposed.

Single crystals of N-benzylaniline (C6H5-CH2-NH-C6H5) have been grown, X-ray structural analysis of these crystals has been performed, and their symmetry has been identified as corresponding to the space group C 2h 5 . Raman spectra of N-benzylaniline single crystals in polarized light for different geometries of the experiment have been analyzed. Frequencies and symmetry of lattice phonons have been determined.

The Raman spectra of virtual ferroelastic Hg2I2 crystals have been studied in a broad range of hydrostatic pressures. Linear pressure dependences of phonon frequencies are obtained at P < P c, which exhibit jumps and breaks at the phase transition point (P c = 9 kbar). Grüneisen parameters of the Hg2I2 crystals are determined. The spectra of a ferroelastic phase (P > P c) in various polarizations exhibit the excitation of new lines from the X point of the Brillouin zone, including transverse (TA) and longitudinal (LA) acoustic phonons. Based on analysis of the experimental and theoretical results, the Raman spectra of ferroelastic Hg2I2 crystals are interpreted and a model of the phase transition in these crystals is proposed.

The dispersion dependences of the frequencies of acoustic and optical phonons have been calculated and plotted, and the density of states of the phonon spectrum of Hg2I2 crystals has been obtained. The influence of hydrostatic pressure on the frequency of acoustic and optical phonons and their dispersion has been theoretically analyzed. The slowest acoustic TA branch (soft mode) at the X point of the Brillouin-zone boundary exhibits strong softening with an increase in pressure.

The Bragg (fundamental) and diffuse reflections from the M-points of the Brillouin zone boundary of the paraphase of the benzyl crystals, whose integrated intensity is related to the order parameter and its fluctuations, respectively, have been investigated. The original information on the temperature behavior of the order parameter and the diffuse scattering is obtained and the values of the corresponding critical exponents are determined. The temperature behavior of the correlation radius and its anisotropy are analyzed. The conclusion is drawn that the phase transition in these crystals is close to the tricritical point. The mechanism of the phase transition in the benzyl crystals alternative to the “trigger” mechanism is suggested.

Bragg and diffuse X-ray reflections from the M points of the Brillouin zone boundary of a benzil crystal paraphrase, the integral intensity of which is associated with the order parameter and its fluctuations, are studied. Original data on the temperature behavior of the order parameter and diffuse scattering are obtained. The relevant critical exponents are determined. A conclusion is drawn as to the proximity of the phase transition in these crystals to the tricritical point. A phase transition model is discussed.

Dispersion relations of the acoustic and optical phonon frequencies have been calculated and plotted, and the density of states of the phonon spectrum of Hg 2 Cl 2 and Hg 2 Br 2 crystals has been derived. The effect of hydrostatic pressure on the frequencies of acoustic and optical phonons and their dispersion has been theoretically analyzed. It has been found that an increase in the pressure leads to a strong softening of the slowest acoustic TA branch (the soft mode) at the X point of the Brillouin zone boundary, which is consistent with the phenomenological Landau theory and correlates with experiment.

Information is obtained about the temperature behavior of the order parameter of a phase transition by theoretical and experimental investigation of odd (acoustic and IR-active) phonons that appear in the Raman scattering spectra from the X points of the Brillouin zone (BZ) boundary in the paraphase of Hg 2 Cl 2 crystals and are induced by the phase transition, unit-cell doubling, and the X → Γ folding in the BZ. The relevant critical exponents are determined, whose values are in agreement with the results of X-ray diffraction measurements and, within the Landau phenomenological theory of phase transitions, indicate that the phase transition in these crystals is close to the tricritical point.