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The hexagonal boron-noble gas compounds B 6 Ng n 4+ (n = 1–6, Ng = He Rn) have been studied theoretically. The geometry, bond energies and thermodynamics properties are reported. For Ar Rn, the B Ng bond length is close to the sum of the covalent radii of B and Ng, the B Ng average bond energy is large up to 59.61–169.43 kcal/mol. There is large charge transfer from Ng to the boron ring, the Ng → boron σ-donation originating from the interaction between the valence p orbital of Ng and the LUMO of the boron ring is the predominant contribution towards the Ng B bond stabilization. The NICS analysis shows that B 6 Ng n 4+ have aromaticity.

In the present work, experimental values of several physical properties for hydrogen halides (including At) are used to obtain, by extrapolation, values of physical properties for tennessine (element 117, Ts) and tennessine hydride (TsH). Using experimental data of Cl, Br, I and At halides, two empirical equations are obtained, allowed us to calculate the ionic and covalent contribution to the bond energy, respectively: E ionic = [μ 2 h/d 3 ]c 2 10 −12 and E covalent = [−22.78P + 400.09] + ν (H X). Using both equations, as well some empirical trends in the Cl, Br, I and At halides, the values of some physical properties of Ts and TsH are estimated. The frequency energy of the Ts H vibration, ν (Ts H), value is calculated as 20.24 kJ mol −1 . For the same bond: μ = 0.24 D; bond distance = 196.76 pm; bond energy = 163.03 kJ mol −1 . The polarizability and covalent radius for Ts are estimated as 11.31/10 −24 cm 3 and 159.76 pm, respectively.

New linear dependences are presented here for the volumes of alkali halides in crystals and in aqueous solutions: (1) the molar volumes in solids ( V B o ) and the partial molal volumes ( ϕ V o ) in aqueous solutions on the sums of crystal ionic volumes, V (M + , X − ) cr , (2) ϕ V o on V B o , (3) ϕ V o on the sum of aqueous ionic volumes, V (M + , X − ) aq and (4) ϕ V o , V B o , V (M + , X − ) cr , V (M + , X − ) aq and volume sum of the hydrated ions, ϕ V o ( M + , X - ) h on the sum of atomic volumes V (M, X) cov based on covalent radii. All ionic radii are based on the Golden ratio. The volumes due to electrostriction and ionic hydration have also been estimated.

The title systems, including EThE′, are treated at DFT level using a B3LYP functional and small-core quasirelativistic pseudopotentials. Most of the studied systems are bent, like their isoelectronic ThO 2 analogue, except for some anionic systems containing Ir. The bond lengths vary considerably and can lie above or below the sum of triple-bond covalent radii. Among the studied systems, the iridium-containing species show the strongest back-donation to Th. The bonding can be simply understood and could theoretically go up to a ‘24-electron principle’ limit at the actinide.

This Letter shows that the ion–water (oxygen) distances for ions of monovalent, divalent and trivalent elements including lanthanides increase linearly with the covalent radii of atoms. The slopes and intercepts of the lines are found to depend on the Golden ratio. The ionic radii in water have been evaluated and ion/water boundaries located. The hydration distances of the oxygen of water to the peripheries of the cations are of four types and are constants. The distance of the hydrogen of water to the peripheries of halogen anions, which is the length of the ‘hydrogen bond’, is also a constant.

The analysis of Mn–chalcogen bond length and of tetrahedral covalent radius of Mn (rtcMn) in AII1−xMnxBVI and in Mn chalcogenides, performed in the previous paper [Chem. Phys. Lett. 350 (2001) 577], was supplemented here by the case of AIII1−xMnxBV (AIII=In, Ga; BV=As, N) compounds. It was found that for chalcogen anions the dependence of rtcMn vs anion atomic number (Aa) can be linearly approximated. Inclusion of the respective rtcMn values for the group-V anions (As, N) reveals their consistency with the above rtcMn(Aa) dependence thus suggesting its more `universal' character.

The analysis of the Mn–chalcogen atom (Te, Se, S) bond lengths in Mn-based AII–BVI and AIV–BVI metal chalcogenides (derived from X-ray absorption fine structure studies) as well as in Mn chalcogenides (from X-ray diffraction (XRD)) enabled the author to introduce certain self-corrections into the papers [Chem. Phys. Lett. 283 (1998) 313; Chem. Phys. Lett. 336 (2001) 226]. In particular, it was found that both the tetrahedral- and octahedral covalent radii of manganese depend on a choice of the anion species in the Mn–chalcogen atom bond, and therefore they cannot be considered as the element constants for Mn.

The bond radius of an atom in a solid is an important parameter since it remains simply correlated with the bond length in a local coordination of the particular crystal structure. The tetrahedral covalent radii of Mn, Fe, Co and Ni were estimated from the measurements of their K-edge extended X-ray absorption fine structure in Zn 1− x M x S (M=Mn, Fe, Co, Ni) alloys. Analysis of these data provided us with the bond lengths of both cationic species (Zn and M) with sulphur. The advantage of the common anion and the knowledge of the tetrahedral radius of Zn enabled us to derive the tetrahedral covalent radii of the transition metals studied.

We have performed cluster calculations in a study of the bonding nature in the CeO2 crystal using the relativistic discrete-variational Xα method. The electron charge distribution of CeO2 is compared with those of ZrO2 and CaF2. The charge density in the metal atomic region indicates stronger covalency for CeO2 than that in Zr for ZrO2. The repulsion between the metal and oxygen ionic cores is, however, strong and superior to the covalent interaction, and thus the ionic character determines the static bonding nature in the CeO2 crystal. A population analysis shows that the mixed interaction due to the independent ionic and covalent contributions arises from the ionic Ce 5s, 5p and covalent Ce 4f, 5d orbitals which are proximate to each other in the bond region.

An empty-core pseudopotential to account for the atomic core and a linearized Fermi-Thomas equation to describe the valence electrons has been formulated previously to treat the simple metals. The covalent bond in semi-conductors is considered in the present work and the Dirac-Fermi-Thomas equation is used to describe the valence electrons. Calculations of the nearest-neighbor distance in fifteen AB covalent compounds with tetrahedral coordination were carried out and it was found that deviations from the experimental values correlate with the ionicity scale defined by Phillips.

It is shown by using the relativistic generalization of spin-valence theory that the j - j coupled ground state of an element having a single valence electron in a Dirac-Fock p or p orbital can form a stable covalent bond to a hydrogen atom. The bond is shown to be a mixture of a normal covalent σ bond and the triplet bond formed by the interaction of two electrons occupying orthogonal orbitals.

An ion at a tetrahedral site will develop an induced octupole moment, which is equivalent to a covalent bond. The magnitude of this bond is calculated For AgI and the copper halides, and removes a discrepancy between theory and experiment which has stood for 47 years.

The model of Parr and Borkman for diatomic molecules is extended to covalent crystals givng dispersion curves in good agreement with experiment for diamond. The relation to Phillips' microscopic dielectric bond-charge theory is discussed.