In 2005 Gagliardi and Roos found the quintuple bond in uranium molecule using computational chemistry. It consists of three strong electron-pair bonds, two fully developed one-electron bonds, two weak one-electron bonds, and two localized electrons. Moreover, in a subsequent paper, Roos et al. defined the effective bond order (EBO) which gives a quantitative measure of the chemical bonding based on molecular orbitals. In this paper, the culture of quantum chemistry and life in Sweden are also briefly touched upon.
The electronic spectra of dinuclear zinc (II) complexes were simulated for [Zn2(μ-H2THBQ)(TPA)2](ClO4)2 (1) and [Zn2(μ-RHOD)(TPA)2](ClO4)2 (2) [H2THBQ2–: 2,3,5,6-tetrahydroxy-1,4-benzoquinonate, TPA: tris (2-pyridylmethyl) amine, RHOD2–: rhodizonate] using the methods of density functional theory (DFT). A band at 361 nm for 1 was assigned to a (2nd HOMO)-LUMO transition, which originates from a bridging benzoquinonate moiety; a band at 502 nm and a band at 449 nm for 2 were assigned to a HOMO-LUMO transition and a HOMO-(2nd LUMO) transition, respectively, and both are originated from a bridging rhodizonate moiety.
Density Functional Theory (DFT) investigations have been conducted for a hexakis-DMF nickel(II) complex cation [Ni(DMF)6]2+ [hexakis(N,N-dimethylformamide-κO)nickel(II)dication] for the purpose of revealing the reasons for the structural features − an S6 symmetry and a trigonal compression − observed by the single-crystal X-ray diffraction experiment, where DMF is an N,N-dimethylformamide molecule as a ligand. The DFT investigations have shown that there are only two conformers − S6 and D3 − for the complex cation [Ni(DMF)6]2+, and the most stable conformer has been found to be the S6 conformer, which is consistent with the crystal structure. In addition, the trigonal compression is reproduced by the DFT computation, indicating that the trigonal compression is the nature of the complex cation but not due to crystal packing. Moreover, inter-ligand hydrogen-bonds have been found to play important roles in determining the structure.
Equations of state (EOS) are proposed for a system involving argon and consisting of a perfect solid and a perfect liquid composed of single spherical molecules in which Lennard–Jones interactions are assumed. Molecular dynamics simulations of this system were performed to determine the temperature and density dependencies of the internal energy and pressure and the supercooled liquid state was also examined. The sum of the average kinetic and potential energies at 0 K and the temperature-dependent potential energy was applied as the internal energy term in the EOS, while the temperature-dependent term of the average potential energy was assumed to be a linear function of the temperature and its coefficient was expressed as a polynomial function of the number density. The pressure was expressed in a similar manner, such that it satisfied the thermodynamic EOS. Using this approach, the equilibrium condition was solved numerically for the phase equilibrium of argon. The Gibbs energy thus calculated gives a reasonable transition pressure for argon's three-phase equilibrium state. The thermodynamic properties at low pressures were found to exhibit significant temperature dependencies.