The lighter group-V element phosphorus forms the As-type (hR2) structure under pressure, above 5 GPa, and at 10 GPa transforms to the simple cubic structure (cP1), similar to arsenic. Despite of its low packing density, the simple cubic structure is stable in phosphorus over a very wide pressure range up to 103 GPa. On further pressure increase, the simple cubic structure transforms to a simple hexagonal structure (hP1) via a complex phase that was solved recently as incommensurately modulated. Structural transformations of Phosphorus are connected with the changes of physical properties. Above 5 GPa phosphorus shows superconductivity with T_c reaching ~9.5K at 32GPa. The crystal structures and properties of high-pressure phases for Phosphorus are discussed within the model of the Fermi sphere and Brillouin zone interactions.

Alexander V. Udal'tsov

Faculty of Biology, Lomonosov Moscow State University, 119899 Moscow, Russia

E-mail: avu151@yandex.ru; avud151@gmail.com

Precursors of microcrystals produced in thin layer of self-organized protonated meso-tetraphenylporphine dimers have been investigated by electronic absorption and infrared spectroscopy, non-contact AFM/SNOM, and SEM to elucidate the role of water and water-soluble organic solvent in the processes of the liquid microcrystals formation [1]. It has been found that tetrahydrofuran (THF) is the most suitable organic solvent providing proton moving through the aqueous acid solution that is required for the formation of liquid micro-crystals. A band around 3200 cm^–1 corresponds to O–O distance ca. 2.63 Å in the O–H⁺...O moiety that is consistent with the distance providing proton sharing [2]. So that characteristic band at 3207 cm^–1 (or a shoulder at 3228 cm^–1 in the presence of HCl), which have been found in IR spectra of THF with small amounts of water, is the prerequisite for the proton moving through water-porphyrin matrix. As evidenced earlier the latter generates the self-organization of the structure [3-4] that is needed for the crystallization. According to AFM/SNOM images, submicroscopic particles consisting of ~ 60-nm particles are covered by a layer of tight water. The tight water was found previously under comparison of the non-contact and contact AFM images [5]. Regular surface of the tight water layer observed by non-contact AFM attests about proton moving through water with the change of the moving direction. The angle of the direction change is sharp, 46.2° or 180°– 46.2°=133.8° depending on the forward or backward proton moving. Tracks of the structure self-organization due to the proton moving observed by SEM on the surface of precursors support this view on the structure self-organization. Similar processes of proton moving through the water-porphyrin matrix are suggested for the prolongation of crystallization germ observed by contact AFM. No crystallization has been found for nanoparticles obtained under the self-assembling of protonated TPP dimers in 7-9% (v/v) aqueous dioxane.

References

[1] A.V. Udal'tsov, J. Crys. Growth. 448 (2016) 6-16.

[2] A.V. Udal'tsov, J. Mol. Spectr. 11 (2017) in press, https://doi.org/10.1016/j.jms.2017.11.008

[3] A.V. Udal'tsov, A.V. Bolshakova, J.G. Vos, J. Mol. Struct. 1080 (2015), 14-23.

[4] A.V. Udal'tsov, J. Mol. Struct. 1084 (2015) 308-318.

[5] A.V. Udal'tsov, M. Tosaka, G. Kaupp, J. Mol. Struct. 660 (2003) 15-23.

In this work we report the synthesis, structural, electronic and magnetic characterization of [Mn^IV₂Mn^II₂(HL)₂(H₂L)₂(H₂O)₄](NO₃)₂  1. This novel compound was obtained from (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl-propane-1,3-diol, (H₄L) and Mn(NO₃)₂. The UV-Vis and IR spectrophotometry showed the typical d-d transitions of Mn^IV in and octahedral geometry compounds ¹ and vibrational transitions in 477 cm^-1, which is assigned to the Mn-O group ². The c_M vs T gave J = 164 cm^{-1 3}. The ESR (g = 11.03, 4.87, 1.78, and g = 3.23, 2.03) analysis of 1 showed the presence of Mn^II (s = 5/2) and Mn^IV (s = 3/2) ions within the molecule. The hyperfine interaction is observed in ESR spectrum which showed two species of Mn ions⁴. An x ray diffraction suitable monocristal of 1 was obtained and its structure was possible to describe as a tetramer of [Mn^IV Mn^II Mn^II Mn^IV] building a 2D stepped supramolecular structure with a step of [Mn^IV–O-O-Mn^II] and a second step with [Mn^II–O-O-Mn^IV]. The structural study informed us that each magnetic box of [Mn^IV-O-O-Mn^II] have a superexchange antiferromagnetic interaction by the d_x2_-y2-sp³ (with more contribution of p orbitals) orbitals; however, among the boxes or steps there is a super-exchange ferromagnetic interaction, by oxo bonds Mn^II-O-Mn^II.

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Microscopic properties of nanocrystal Aluminum thin film have been simulated using the quasicontinuum method in order to study the surface defect influence in nanoindentation. Various distances between the surface defect and indenter have been taken into account. The results show that as the distance between the pit and indenter increases, the nanohardness increases in a wave pattern associated with a cycle of three atoms, which is closely related to the crystal structure of periodic atoms arrangement on {111} atomic close-packed planes of face-centered cubic metal; when the adjacent distance between the pit and indenter is more than 16 atomic spacing, there is almost no effect on nanohardness. In addition, the theoretical formula for the necessary load for elastic-to-plastic transition of Al film has been modified with the initial surface defect size, which may contribute to the investigation of material property with surface defects.

We report the crystal structure of [Zn₂Ho^III(L)(ald)(HO)(H₂O)₃(MeCN)](NO₃)₂·EtOH [being H₃L = 2-(5‑bromo-2-hydroxy-3-methoxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxy-3-methoxy phenyl)-3-azabut-3-enyl]-1,3-imidazolidine); and Hald = 5‑bromo-2-hydroxy-3-methoxybenzaldehyde]. Despite the presence of two bulky multidentate ligands, as well as several monodentate ligands surrounding the nonacoordinated holmium cation, and the two pseudooctahedral zinc ions, the intricate H-bonded system formed by this chiral heterotrinuclear complex is only expanded in a 2D supramolecular structure. The interactions involve the nitrate counterions and the solvated ethanol, in such way that each complex unit is connected to an identical enantiomer, and to two units of inverted chirality through H bonds

The search for spin-polarized metal clusters, energetic crystals and conductive materials is a paramount part of Nanotechnology. Adapting quantum chemistry and quantum mechanics methods to study and endeavor the electronic and lattice properties of groups of atoms in nanoclusters is a central approach, which aids in revealing crucial electronic properties that serve to develop and synthesize nanomaterials, nanometals and metal clusters. This project investigates the energy landscape of Niobium clusters (Nb_n), in order to shed light on its electronic, dipole, and magnetic properties. The clusters are studied with the XTB Tight-binding software coupled with hybrid DFT functionals. The results show that Niobium clusters in nanosized particles (10-61 atoms) bear ultra-low orbital gaps, with promising properties for hyperconnects and nanoparticle based electronics.

Reaction of 2-cyanopyridine with N-phenylthiosemicarbazideafforded the 4-phenyl-5-(pyridin-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione. Methyl 2-((4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl)thio)acetate (phpy2NS, 1), derived from this 1,2,4-triazole-3-thione, was obtained by reaction with chloroacetic acid followed by an acid-catalyzed esterification of the carboxylic acid with methyl alcohol. Synthesis of a Hg(II) complex, [Hg(phpy2NS)Cl₂] (2), has been performed using the ligand (1) and HgCl₂. The molecular and supramolecular structures of the ligand and the complex, were studied by X-ray diffractometry.

A new technique of liquid phase epitaxy (LPE) has been proposed in this work. It allows to eliminate known disadvantages of LPE by creating short-time contact between a substrate and a solution-melt, as well as due to segmental deposition of an epitaxial layer over the working substrate surface. The short-time of the contact is achieved by the means of Ampere force acting on the solution-melt. And the contact itself between the substrate and the solution-melt is realized pointwise (or segmentally) over the substrate surface using the scanning principle. The new technique was named "scanning liquid phase epitaxy". One of the modifications of device realization of the technique proposed has been considered and its principle of operation has been described. Preliminary theoretical investigations and experimental processes of semiconductor epitaxial layers obtaining have proved principal operational capability of the new technique. The technique developed allows to obtain thin and ultrathin epitaxial layers on the substrates of very large area which is limited only by the growth equipment size.

An order to disorder transitions are important for 2D objects such as oxide films with cellular porous structure, honeycomb, graphene, Bénard cells in liquid and artificial systems consisting of colloid particles on a plane. For instance, solid films of the porous alumina represent almost regular quasicrystal structure. We show that in this case the radial distribution function is well described by the quasicrystal model [1], i.e. the smeared hexagonal lattice of the two dimensional ideal crystal with inserting some amount of defects into the lattice. Another example is a system of the hard disks in a plane which illustrates the order to disorder transitions. It is shown, that the coincidence with the distribution function, obtained by the solution of the Percus-Yevick equation is achieved by the smoothing of the square lattice and injecting the defects of the vacancy type into it. However, better approximation is reached when the lattice is a result of a mixture of the smoothened square and hexagonal lattices. Impurity of the hexagonal lattice is considerable at the short distances. Dependences of the lattices constants, smoothing widths and impurity on the filling parameter are found. Transition to the order looks as an increasing of the hexagonal lattice contribution and decreasing of smearing.

           [1] Cherkas, N.L. & Cherkas, S.L. Crystallogr. Rep. (2016) 61: 285. https://doi.org/10.1134/S106377451506005X

The structure of metallomesogens complexes differs essentially from that of calamitic liquid crystals that emerges in their physical properties. We studied anomalous features of the transition from nematic to isotropic phase (N-I) in the ytterbium-based liquid crystal complex. For this, two approaches were used.  At first approach, we showed that the experimental values of the dielectric and optical anisotropies measured near the phase transition turned out to be substantially smaller than their calculated values. This is evidently taken place because the phase transition temperature in the deep of the experimental cell differs from that near the surface of the cell. Secondly, the temperature of N-I transitions in metallomesogenic layers being within glass sandwich cells is obtained directly by means of the polarization microscope method. It was found that the phase transition temperature drops in more than ten degrees when reducing of metallomesogenic layer thick form 200 to 5 microns. The calamite liquid crystals show the confinement effect only within interstice of the specific size smaller than one micron. An anomalous confinement effect can be caused by a strong interaction of the complexes with each other.