Blue Circularly Polarized Luminescent Amorphous Molecules with Single-handed Propeller Chirality Induced by Circularly Polarized Light Irradiation

Preferred-handed propeller conformation was induced by circularly polarized light irradiation to three amorphous molecules with trigonal symmetry, and the molecules with induced chirality efficiently exhibited blue circularly polarized luminescence. In...

Investigations on the g factors and local structure for the trigonal Ce3+ center in YAl3(BO3)4 crystal

The perturbation formulae of the EPR gyromagnetic factors g// and g⊥ for the lowest Kramers doublet of a 4f1 ion in trigonal symmetry are established. By using the above perturbation formulae, the anisotropic g factors and the local structure for the trigonal Ce3+ center in YAl3(BO3)4 crystal are theoretically studied. From the studies, this center is attributed to the impurity Ce3+ occupying the trigonal prism Y3+ site in YAl3(BO3)4. The Ce3+–O2− bond is found to undergo an angular variation Δθ(≈ 1.72°) related to the C3 axis. The calculated g factors based on the above impurity angular distortion display consistence with the measured results. The anisotropic g factors and the trigonal distortion of the Ce3+ center are analyzed with respect to the host Y3+ site in YAl3(BO3)4.

Пути политипных превращений в карбиде кремния

In this work, two main polytypic transformations in silicon carbide, namely, 2H→6H and 3C→6H, were studied using ab initio methods. It is shown that intermediate states with trigonal symmetry P3m1 and monoclinic symmetry Cm greatly simplify the movement of close-packed layers during such transitions, breaking them up into separate stages. It was found that the two polytypic transformations occur quite differently. During the 2H→6H transition, the displaceable bonds are noticeably tilted compared to the initial position, which makes it possible to reduce the compression of SiC bonds in the (112 ̅0) plane. The 3C→6H transition takes place through the formation of auxiliary Si – Si and C – C bonds that live for a short time and help the tightly packed layers exchange places. As a result, the activation barrier for the conversion of 2H→6H (1.7 eV/atom) is significantly less than the activation barrier for the conversion of 3C→6H (3.6 eV/atom), which means that the second transition must occur at temperatures of 750-800 ℃ higher than the first one. The energy profiles of these polytypic transformations, as well as the geometry of all intermediate and transitional phases, are calculated. It is shown that all transition states have monoclinic symmetry.

Investigation of the magnetic anisotropy in a series of trigonal bipyramidal Mn(ii) complexes

The trigonal symmetry around the MnII ion is fine-tuned to control the rhombic zero-field splitting.

Trigonal columnar self-assembly of bent phasmid mesogens

Three compounds with a bent rod-like core are shown to form the first columnar liquid-crystal phase with confirmed non-centrosymmetric trigonal symmetry.

Structural and compositional variations of basic Cu(II) chlorides in the herbertsmithite and gillardite structure field

Natural samples of the substituted basic Cu(II) chloride series, Cu4–xMx2+(OH)6Cl2(M = Zn, Ni, or Mg) were investigated by single-crystal X-ray diffraction in order to elucidate compositional boundaries associated with paratacamite and its congeners. The compositional ranges examined are Cu3.65Zn0.35(OH)6Cl2 – Cu3.36Zn0.64(OH)6Cl2 and Cu3.61Ni0.39(OH)6Cl2 – Cu3.13Ni0.87(OH)6Cl2, along with a single Mg-bearing phase. The majority of samples studied have trigonal symmetry (R3̄m) analogous to that of herbertsmithite (Zn) and gillardite (Ni), with a ≈ 6.8, c ≈ 14.0 Å. Crystallographic variations for these samples caused by composition are compared with both published and new data for the R3̄m sub-cell of paratacamite, paratacamite-(Mg) and paratacamite-(Ni). The observed trends suggest that the composition of end-members associated with the paratacamite congeners depend upon the nature of the substituting cation.

Structure and luminescence properties of a Nd3+doped Bi4Ge3O12scintillation crystal: new insights from a comprehensive study

We have, for the first time, identified a unique semiconducting phase of theR3 space group where impurity Nd3+ions occupy exactly the host Bi3+ion sites with trigonal symmetry.

Revisiting the (E + A) ⊗ (e + a) problems of polyatomic systems with trigonal symmetry: general expansions of their vibronic Hamiltonians

In this work, we derive general expansions in vibrational coordinates for the (E + A) ⊗ (e + a) vibronic Hamiltonians of molecules with one and only one C3 axis.