Quantum Coherence of Atoms with Dipole–Dipole Interaction and Collective Damping in the Presence of an Optical Field

We investigate the effect of the interatomic distances and thermal reservoir on the coherence dynamics of the atoms considering the dipole–dipole interaction (DDI) and collective damping effect (CDE). We show that the control and protection of the coherence are very sensitive to the interatomic distances and reservoir temperature. Furthermore, we explore the distance effect between atoms and reservoir temperature on the time evolution of the total quantum correlation between the two atoms. The obtained results could be useful to execute these quantum phenomena and also considered as a good indication to implement realistic experiments with optimal conditions.

First Principles Calculations of Atomic and Electronic Structure of TiAl3+- and TiAl2+-Doped YAlO3

In this paper, the density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of the Ti3+ and Ti2+ ions substituted for the host Al atom in orthorhombic Pbnm bulk YAlO3 crystals. The disordered crystalline structure of YAlO3 was modelled in a large supercell containing 160 atoms, allowing simulation of a substitutional dopant with a concentration of about 3%. In the case of the Ti2+-doped YAlO3, compensated F-center (oxygen vacancy with two trapped electrons) is inserted close to the Ti to make the unit cell neutral. Changes of the interatomic distances and angles between the chemical bonds in the defect-containing lattices were analyzed and quantified. The positions of various defect levels in the host band gap were determined.

Decomposition CO₂ and CO in Flow of Gases by Means of Technical Ferrogravitational Field

The author's experimental studies shown that magnetic poles (magnetic charges) are real structural components of atoms and substance. It is the magnetic poles, and not the electrons moving are direct sources of all magnetic fields in nature. The main reasons for ignoring magnetic charges in physical science are the hard conditions for their confinement in the structures of substance which is fundamentally different from the confinement of electrons, as well as the vicious electric magnetism of Maxwell (1873). True magnetic poles have been “buried alive” in physical theory under such theoretical surrogates as the magnetic moments of electrons. The electromagnetic shells of atoms composed of electric and magnetic charges are the sources of gravitational field which is the vortex electromagnetic field and is described by vortex vector rot[E – H]. Depending on the state of vortex vectors rot[E – H] in the composition of gravitational fields (GF) emitted by atoms, these fields are subdivided into paragravitational (PGF) and ferrogravitational (FGF). The sources of ferrogravitational field are repelled from sources of paragravitational field, for example, from Earth. The forces of such repulsion depend on the degree ferropolarization of gravitational field of atom - source of FGF, and the physical manifestation such repulsion is еthe effect of the ferrogravitational levitation (FGL), which discovered and investigated by the author. The FGL effect is also realized between the atoms emitting PGF and FGF in the formulations of chemical compounds. When an external FGF acts on CO2 molecule the process ferropolarization of gravitational field of oxygen atom is realized, which should be defined as the gravito-plastic source. In this case, the carbon atom, which is the gravito-stable mass, remains of paragravitational. At interatomic distances <1 Å the forces of the gravito-levitation repulsion may be very significant and lead to the rupture of chemical bonds between oxygen and carbon atoms and to the disintegration of the molecule CO2. It is highly probable that the process of decomposition of CO2, similar to that described above, is carried out in the cells of leaves of green plants, which emit precisely the ferrogravitational field. The decomposition of CO2 by FGF and the supply of oxygen to green plants is natural process that takes place in leaf cells called photosynthesis. However, photons in this process are only a stimulating factor contributing to the ferropolarization of gravitational field emitted by atoms oxygen in the composition of green plant cells.

Ba5(IO6)2: crystal structure evolution from room temperature to 80 K

The crystal structure of Ba5(IO6)2, pentabarium bis(orthoperiodate), has been re-investigated at room temperature based on single-crystal X-ray diffraction data. In comparison with a previous crystal structure determination by the Rietveld method, an improved precision of the structural parameters was achieved. Additionally, low-temperature measurements allowed the crystal structure evolution to be studied down to 80 K. No evidence of structural transition was found even at the lowest temperature. Upon cooling, the lattice contraction is more pronounced along the b axis. This contraction is found to be inhomogeneous along different crystallographic axes. The interatomic distances between different Ba atoms reduce drastically with lowering temperature, resulting in a closer packing around the IO6 octahedra, which remain largely unaffected.

Site-occupancy scheme in disordered Ca3RE2(BO3)4: a dependence on rare-earth (RE) ionic radius

The structures of polycrystalline Ca3RE2(BO3)4 (RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y; space group Pnma) orthoborates were determined using powder X-ray diffraction. Trends in the unit-cell dimensions and yet unreported trends in other structural properties (interatomic distances and the fractional occupation of three Ca/RE sites) for these compounds are demonstrated as a function of RE ionic radius. The unit-cell volume and a unit-cell parameter present a linear dependence, while the b and c unit-cell parameters change in a nonlinear manner. For the whole series, the RE atoms are present at all three cationic sites (labelled as M1, M2 and M3), but the fractional occupancies depend on the RE ionic radius. The small rare-earth atoms tend to enter mainly the M3 site; for the larger rare earths, the occupancy of this site decreases sharply. The occupancy of the M1 site by RE atoms is around 0.5 and tends to increase with increasing RE ionic radius. The M2 site is the least preferentially occupied by RE ions, but the occupancy discernibly increases with rising radius as well. These findings are assembled with properties of isostructural strontium and barium borates, allowing prediction of occupancy schemes for not yet investigated compounds from the A 3RE2(BO3)4 (A = Ca, Ba, Sr).

Quantum Calculations on Ion Channels: Why Are They More Useful Than Classical Calculations, and for Which Processes Are They Essential?

There are reasons to consider quantum calculations to be necessary for ion channels, for two types of reasons. The calculations must account for charge transfer, and the possible switching of hydrogen bonds, which are very difficult with classical force fields. Without understanding charge transfer and hydrogen bonding in detail, the channel cannot be understood. Thus, although classical approximations to the correct force fields are possible, they are unable to reproduce at least some details of the behavior of a system that has atomic scale. However, there is a second class of effects that is essentially quantum mechanical. There are two types of such phenomena: exchange and correlation energies, which have no classical analogues, and tunneling. Tunneling, an intrinsically quantum phenomenon, may well play a critical role in initiating a proton cascade critical to gating. As there is no classical analogue of tunneling, this cannot be approximated classically. Finally, there are energy terms, exchange and correlation energy, whose values can be approximated classically, but these approximations must be subsumed within classical terms, and as a result, will not have the correct dependence on interatomic distances. Charge transfer, and tunneling, require quantum calculations for ion channels. Some results of quantum calculations are shown.

Evidence for Local Structural Distortion and Mixed States of Fe in β-NaFeO2: A Bond Valence Sum Analysis

We have analyzed the crystal structure, interatomic distances and bond valence sums in β-phase of sodium ferrite based on neutron diffraction measurement at room temperature. The Rietveld analysis performed using Pna21 space group obtains smaller lattice constants compared to the previous reports. This discrepancy is attributed to the sodium deficiency. We notice that the Na-O bonds are shortened, while Fe-O bonds are elongated. The calculated bond valence sum around the sodium and the iron ions are 1.08 and 2.64, respectively. This indicates the presence of Fe2+-Fe3+ mixed valence state.

Spin-induced negative thermal expansion and spin–phonon coupling in van der Waals material CrBr3

The two-dimensional van der Waals (vdW) magnets retaining magnetic order in atomically thin limit demonstrate challenging physical phenomena and they are considered as prospective building blocks for construction of advanced spintronics and nanoelectronics devices. Here, we present experimental evidence for negative thermal expansion of lattice volume and vdW layers and strong spin–phonon coupling effects, caused by formation of the long-range ferromagnetic order in the vdW material CrBr3. The neutron and X-ray diffraction measurements revealed anomalous temperature variation of lattice parameters and interatomic distances and angles in the vicinity of Curie temperature (TC). A pronounced rise of the frequencies of the most of the observed vibrational modes and unusual reversal broadening of their full widths at half maximum below TC was found from Raman spectroscopy measurements.