Simplified time-dependent self-consistent field approximation for intramolecular dynamics

The time-dependent Hartree approximation is applied to intramolecular dynamics of polyatomics with smooth, locally quadratic potential surfaces. It is shown that the full quantum solution is obtained from a certain single self-consistent trajectory. An extremely simple model results, pertinent to intramolecular energy transfer, vibrational lineshapes and unimolecular decay.     

Photoionization of the Ar2 dimer

The relative photoionization cross section for Ar₂ was measured in the wavelength region 820–860 Å. The spectrum shows detailed autoionization structure throughout this region with no contribution from direct ionization. The appearance potential of Ar⁺₂ corresponds to 856.5 ± 1.5 Å.     

Theoretical study of the visible photodissociation spectrum of Ar3

The six A′ potential energy surfaces were computed by a DIM-like method involving a valence-bond quasidiabatic basis. Transition dipole moments were also determined using a similar method. The 4D dynamics of this system (restricted to a molecular plane fixed in space) was obtained with the HWD method (hemiquantal dynamics with the whole DIM basis) and the visible photoabsorption spectrum was determined with the help of a 1D full quantum mechanical program applied to each normal mode. The photoabsorption spectrum of Ar₃⁺ was calculated in the range 440–710 nm. It corresponds to photodissociation since the excited Ar₃⁺ ions almost all dissociate into the Ar⁺ +Ar+Ar channel by a rapid explosion of the cluster, and only very few into Ar₂⁺ +Ar. It is dominated by a transition to the second excited state along with a symmetric stretching motion. We found a prominent 80 nm wide peak centered at 530 nm, with a maximum cross section of 4.2 × 10⁻¹⁶cm². The Ar₂⁺ formation results from a transition to the first excited state under low-energy laser excitation and is controlled by non-adiabatic transitions.     

Dissociation energy of the NH3 · Hg(P0) complex

A phase-shift method has been used to study the bimolecular and termolecular reactions of Hg(³P₀) with NH₃. The bimolecular and termolecular rate constants are 3.8 × 10⁻¹³ cm³ molecule⁻¹sec⁻¹ and 1.4 × 10⁻³⁰ cm⁶ molecule⁻²sec⁻¹, respectively. From the difference between the wavelengths of peak emission intensity for the stabilized and unstabilized Hg·NH₃ complexes the dissociation energy of the complex is estimated to be 5.0 kcal mole⁻¹.     

Nonvariational time-dependent multiconfiguration self-consistent field equations for electronic dynamics in laser-driven molecules

A time-dependent multiconfiguration self-consistent field (TDMCSCF) scheme is developed to describe the time-resolved electron dynamics of a laser-driven many-electron atomic or molecular system, starting directly from the time-dependent Schrodinger equation for the system. This nonvariational formulation aims at the full exploitations of concepts, tools, and facilities of existing, well-developed quantum chemical MCSCF codes. The theory uses, in particular, a unitary representation of time-dependent configuration mixings and orbital transformations. Within a short-time, or adiabatic approximation, the TDMCSCF scheme amounts to a second-order split-operator algorithm involving generically the two noncommuting one-electron and two-electron parts of the time-dependent electronic Hamiltonian. We implement the scheme to calculate the laser-induced dynamics of the two-electron H2 molecule described within a minimal basis, and show how electron correlation is affected by the interaction of the molecule with a strong laser field.     

Crystal structure and lattice dynamics of Sr3Y(BO3)3

X-ray, Raman and infrared (IR) studies of the Sr₃Y(BO₃)₃ (BOYS) single crystal grown by the Czochralski technique are presented. The crystal structure is trigonal, space group (no. 148), and comprises six formula units in the unit cell with the hexagonal axes a=12.527(2) and c=9.280(2) Å. The assignment of the observed vibrational modes is proposed on the basis of lattice dynamics calculations. The unusual large bandwidth of the internal modes and the enhancement of the principal mean square thermal displacements for BO₃ and Y(1) indicate that some type of disorder is present in the studied crystal.     

Exponentially divergent trajectories and RRKM behaviour of Ar3 clusters

The rate of exponential divergence of two initially adjacent trajectories has been studied for Ar₂ clusters at low and high energies. It is found that at the dissociation limit energy randomization occurs during two typical vibrational periods. Lifetime distributions for energies not far above the dissociation limit have a random lifetime pattern but highly energized clusters show non-RRKM behaviour     

Structure of two new borates YCa3(AlO)3(BO3)4 and YCa3(GaO)3(BO3)4

By replacing Mn in YCa₃(MnO)₃(BO₃)₄ with trivalent Al and Ga, two new borates with the compositions of YCa₃(MO)₃(BO₃)₄ (M=Al, Ga) were prepared by solid-state reaction. Structure refinements from X-ray powder diffraction data revealed that both of them are isostructural to gaudefroyite with a hexagonal space group P6₃/m. Cell parameters of a=10.38775(13)Å, c=5.69198(10)Å for the Al-containing compound and a=10.5167(3)Å, c=5.8146(2)Å for the Ga analog were obtained from the refinements. The structure is constituted of AlO₆ or GaO₆ octahedral chains interconnected by BO₃ groups in the ab plane to form a Kagomé-type lattice, leaving trigonal and apatite-like tunnels. It is found that most rare-earth and Cr, Mn ions can be substituted into the Y³⁺ and M³⁺ sites, respectively, and the preference of rare-earth ions to locate in the trigonal tunnel is correlated to the sizes of the M³⁺ ions.     

Synthesis and characterisation of HRuRh3(CO)12. Crystal structures of HRuRh3(CO)12, HRuRh3(CO)10(PPh3)2 and HRuCo3(CO)10(PPh3)2

A new ruthenium-rhodium mixed-metal cluster HRuRh₃(CO)₁₂ and its derivatives HRuRh₃(CO)₁₀(PPh₃)₂ and HRuCo₃(CO)₁₀(PPh₃)₂ have been synthesized and characterized. The following crystal and molecular structures are reported: HRuRh₃(CO)₁₂: monoclinic, space group P2₁/c, a 9.230(4), b 11.790(5), c 17.124(9) Å, β 91.29(4)°, Z = 4; HRuRh₃(CO)₁₀(PPh₃)₂·C₆H₁₄: triclinic, space group P$\text{1}$, a 11.777(2), b 14.079(2), c 17.010(2) Å, α 86.99(1), β 76.91(1), γ 72.49(1)°, Z = 2; HRuCo₃(CO)₁₀(PPh₃)₂·CH₂Cl₂: triclinic, space group P$\text{1}$, a 11.577(7), b 13.729(7), c 16.777(10) Å, α 81.39(4), β 77.84(5), γ 65.56°, Z = 2. The reaction between Rh(CO)₄^? and (Ru(CO)₃Cl₂)₂ tetrahydrofuran followed by acid treatment yields HRuRh₃(CO)₁₂ in high yield. Its structural analysis was complicated by a 80–20% packing disorder. More detailed structural data were obtained from the fully ordered structure of HRuRh₃(CO)₁₀(PPh₃)₂, which is closely related to HRuCo₃(CO)₁₀(PPh₃)₂ and HFeCo₃(CO)₁₀(PPh₃)₂. The phosphines are axially coordinated.     

Vaporization of DyI3(s) and thermochemistry of the homocomplexes (DyI3)2(g) and (DyI3)3(g)

The vaporization of DyI₃(s) was investigated in the temperature range between 833 and 1053 K by the use of Knudsen effusion mass spectrometry. The ions DyI₂⁺, DyI₃⁺, Dy₂I₄⁺, Dy₂I₅⁺, Dy₃I₇⁺, and Dy₃I₈⁺ were detected in the mass spectrum of the equilibrium vapor. The gaseous species DyI₃, (DyI₃)₂, and (DyI₃)₃ were identified and their partial pressures determined. Enthalpies and entropies of sublimation resulted according to the second- and third-law methods. The following sublimation enthalpies at 298 K were determined for the gaseous species given in brackets: 274.8±8.2 kJ mol⁻¹ [DyI₃], 356.0±11.3 kJ mol⁻¹ [(DyI₃)₂], and 436.6±14.6 kJ mol⁻¹ [(DyI₃)₃]. The enthalpy changes of the dissociation reactions (DyI₃)₂=2 DyI₃ and (DyI₃)₃=3 DyI₃ were obtained as Δ_dH°(298)=193.3±5.6 and 390.3±13.0 kJ mol⁻¹, respectively.     

Direct dynamics studies on the hydrogen abstraction reactions CF3O+CH4(CD4)→CF3OH(CF3OD)+CH3(CD3)

The dynamics properties of the hydrogen abstraction reaction CF₃O+CH₄→CF₃OH+CH₃ are studied by dual-level direct dynamics method. Optimization calculations are preformed by B3LYP and MP2 with the 6-311G(d,p) basis set, and the single-point calculations are done at the multi-coefficient correction method based on quadratic configuration interaction with single and double excitations (MC-QCISD) method. The rate constants are evaluated by canonical variational transition-state theory with a small-curvature tunneling correction over a wide range of temperature 200–2000 K. The agreement between theoretical and experimental rate constants is good in the measured temperature range. The calculated results show that the variational effect is small and almost neglected over the whole temperature range, whereas, the tunneling correction plays a role in the lower temperature range. The kinetic isotope effect for the reaction is ‘normal’. The value of k_H/k_D is 2.38 at room temperature and it decreases with the temperature increasing.     

Proton dynamics in superionic phase of Tl3H(SO4)2

Electrical properties and ¹H-NMR absorption line have been measured, in order to investigate proton dynamics in a superionic phase in Tl₃H(SO₄)₂. From the measurement of the thermoelectric power, it is found that a majority carrier in electrical conductivity is a proton. Moreover, from ¹H-NMR measurement it is also found that the activation energy 0.33 eV of the hopping motion of protons is close to 0.38 eV as observed in the electrical conductivity measurement. These results indicate that the electrical conductivity in the superionic phase is caused by the hopping motion of protons accompanied by the breaking of the hydrogen bonds.     

Conductivities of the Ternary Systems Y(NO3)3+La(NO3)3+H2O, La(NO3)3+Ce(NO3)3+H2O, La(NO3)3+Nd(NO3)3+H2O and Their Binary Subsystems at Different Temperatures

Electrical conductivities were measured for the ternary systems Y(NO₃)₃+La(NO₃)₃+H₂O, La(NO₃)₃+Ce(NO₃)₃+H₂O, La(NO₃)₃+Nd(NO₃)₃+H₂O, and their binary subsystems Y(NO₃)₃+H₂O, La(NO₃)₃+H₂O, Ce(NO₃)₃+H₂O, and Nd(NO₃)₃+H₂O at (293.15, 298.15 and 308.15) K. The measured conductivities were used to test the generalized Young’s rule and the semi-ideal solution theory. The comparison results show that the generalized Young’s rule and the semi-ideal solution theory can yield good predictions for the conductivities of the ternary electrolyte solutions, implying that the conductivities of aqueous solutions of (1:3 + 1:3) electrolyte mixtures can be well predicted from those of their constituent binary solutions by the simple equations.     

Magnetic investigation of Cu(NH3)4(NO3)2

The magnetic properties of Cu(NH₃)₄(NO₃)₂ have been measured at low temperatures. Broad maxima in both the susceptibility and specific heat are observed and are consistent with linear chain behavior of a Heisenberg antiferromagnet, with J/k = 3.9 ± 0.1 K. Long-range order sets in at T_c = 0.15 ± 0.01 K, and the ratio kT_c/|J| = 0.038 is the lowest observed as yet for a one-dimensional, S = 1/2 antiferromagnet.     

Hydrothermal Syntheses, Structures, and Properties of Two New Potassium Vanadium Phosphates: K3(VO) (V2O3) (PO4)2(HPO4) and K3 (VO) (HV2O3) (PO4)2(HPO4)

Two new potassium vanadium phosphates have been prepared and their structures have been determined from analysis of single crystal X-ray data. The two compounds, K₃(VO)(V₂O₃) (PO₄)₂(HPO₄) and K₃(VO)(HV₂O₃)(PO₄)₂(HPO₄), are isostructural, except for the incorporation of an extra hydrogen atom into the nearly identical frameworks. The structures consist of a three-dimensional network of [VO]_n chains connected through phosphate groups to a [V₂O₃] moiety. Magnetic susceptibility experiments indicate that in the case of the di-hydrogen compound, there are no significant magnetic interactions between the three independent vanadium (IV) centers. Crystal data: for K₃(VO)(V₂O₃)(PO₄)₂ (HPO₄), M_r = 620.02, orthorhombic space group Pnma (No. 62), a = 7.023(4) Å, b = 13.309(7) Å, c = 14.294(7) Å, V = 1336(2) ų, Z = 4, R = 5.02%, and R_w = 5.24% for 1238 observed reflections [I > 3σ(I)]; for K₃(VO)(HV₂O₃)(PO₄)₂(HPO₄), M_r = 621.04, orthorhombic space group Pnma (No. 62), a = 6.975(3) Å, b = 13.559(7) Å, c = 14.130(7) Å, V = 1336(1) ų, Z = 4, R = 6.02%, and R_w = 6.34% for 1465 observed reflections [I > 3σ(I)].     

Luminescence properties of efficient X-ray phosphors of YBa3B9O18, LuBa3(BO3)3, α-YBa3(BO3)3 and LuBO3

The samples of YBa₃B₉O₁₈, LuBa₃(BO₃)₃, α-YBa₃(BO₃)₃ and LuBO₃ powders have been synthesized by the solid-state reaction methods at high temperature and their X-ray excited luminescent properties were investigated. All the studied materials show a broad emission band in the wavelength range of 300-550 nm with the peak centers at about 385 nm for YBa₃B₉O₁₈ and LuBa₃(BO₃)₃, 415 nm for α-YBa₃(BO₃)₃ and 360 nm for LuBO₃ powders, respectively. Even though those compounds have the different atomic structures, they have the common structural feature of each yttrium or lutetium ion bonded to six separate BO₃ groups, i.e., octahedral RE(BO₃)₆ (RE=Lu or Y) moiety. This octahedral RE(BO₃)₆(RE=Lu or Y) moiety seems to be an important structural element for efficient X-ray excited luminescence of those compounds, as are the edge-sharing octahedral TaO₆ chains for tantalate emission.     

Syntheses, structures, and properties of Ag4(Mo2O5)(SeO4)2(SeO3) and Ag2(MoO3)3SeO3

Ag₄(Mo₂O₅)(SeO₄)₂(SeO₃) has been synthesized by reacting AgNO₃, MoO₃, and selenic acid under mild hydrothermal conditions. The structure of this compound consists of cis-MoO₂²⁺ molybdenyl units that are bridged to neighboring molybdenyl moieties by selenate anions and by a bridging oxo anion. These dimeric units are joined by selenite anions to yield zigzag one-dimensional chains that extended down the c-axis. Individual chains are polar with the C₂ distortion of the Mo(VI) octahedra aligning on one side of each chain. However, the overall structure is centrosymmetric because neighboring chains have opposite alignment of the C₂ distortion. Upon heating Ag₄(Mo₂O₅)(SeO₄)₂(SeO₃) looses SeO₂ in two distinct steps to yield Ag₂MoO₄. Crystallographic data: (193 K; MoKα, λ=0.71073 Å): orthorhombic, space group Pbcm, a=5.6557(3), b=15.8904(7), c=15.7938(7) Å, V=1419.41(12), Z=4, R(F)=2.72% for 121 parameters with 1829 reflections with I>2σ(I). Ag₂(MoO₃)₃SeO₃ was synthesized by reacting AgNO₃ with MoO₃, SeO₂, and HF under hydrothermal conditions. The structure of Ag₂(MoO₃)₃SeO₃ consists of three crystallographically unique Mo(VI) centers that are in 2+2+2 coordination environments with two long, two intermediate, and two short bonds. These MoO₆ units are connected to form a molybdenyl ribbon that extends along the c-axis. These ribbons are further connected together through tridentate selenite anions to form two-dimensional layers in the [bc] plane. Crystallographic data: (193 K; MoKα, λ=0.71073 Å): monoclinic, space group P2₁/n, a=7.7034(5), b=11.1485(8), c=12.7500(9) Å, β=105.018(1) V=1002.7(2), Z=4, R(F)=3.45% for 164 parameters with 2454 reflections with I>2σ(I). Ag₂(MoO₃)₃SeO₃ decomposes to Ag₂Mo₃O₁₀ on heating above 550 °C.     

Electric field gradients in the ionic crystals NaNO2, NaBF4, NaNO3, and Ba(NO3)2

The electric field gradients (EFG) at the sites of the cations and the “central” atoms of the anions in the ionic crystals NaNO₂, NaBF₄, NaNO₃ and Ba(NO₃)₂ are calculated by a method based on a combination of the semi-empirical INDO method for the charge distribution and the intramolecular EFG with a lattice summation in the framework of the extended multipole model. At some lattice sites the contribution of the induced dipole and quadrupole moments to the EFG is comparable with the contribution of the point charges. The charge distribution within the molecular ions is found by adjusting either the calculated asymmetry parameter η or the z-component of the EFG to the experimental value deduced from nuclear quadrupole coupling constants. These charge distributions are in good agreement with those gained from INDO calculations. The calculated and experimental quadrupole coupling constants of nuclei in anions and cations are compared.     

Vibrational spectra of the peroxotantalates (NH4)3[Ta(O2)4], K3[Ta(O2)4], Rb3[Ta(O2)4] and Cs3[Ta(O2)4] and the crystal structure of Rb3[Ta(O2)4]

The compounds (NH₄)₃[Ta(O₂)₄], K₃[Ta(O₂)₄], Rb₃[Ta(O₂)₄] and Cs₃[Ta(O₂)₄] have been prepared and investigated by X-ray powder methods as well as Raman- and IR-spectroscopy. In the case of Rb₃[Ta(O₂)₄] the structure has been solved from single crystal data. It is shown that all these compounds are isotypic and crystallize in the K₃[Cr(O₂)₄] type (SG , No. 121). The infrared- and Raman spectra (recorded on powdered samples) are discussed with respect to the internal vibrations of the peroxo-group and the dodecahedral [Ta(O₂)₄]³⁻ ion. Symmetry coordinates for the [Ta(O₂)₄]³⁻ ion are given from which the vibrational modes of the O-O stretching vibrations of the O₂²⁻ groups, the Ta-O stretching vibrations and the Ta-O bending vibrations are deduced.     

The reaction of Ru3(CO)12 and Os3(CO)12 with PH2Ph; the x-ray crystal structures of HRu3(CO)10(PHPh) and H2Ru3(CO)9(PPh)

Twelve new trinuclear complexes containing terminal PH₂Ph, edge-bridging PHPh and/or capping PPh ligands have been isolated from the reaction of M₃(CO)₁₂ (M = Ru or Os) with PH₂Ph in refluxing solvents. HRu₃(CO)₁₀(PHPh) (IIIa) crystallises in the monoclinic space group P2₁/c with a = 8.761(3), b = 11.402(4), c = 22.041(7) Å,β = 98.89(2)°, and Z = 4. The structure was solved by a combination of direct methods and Fourier difference techniques, and refined by blocked-cascade least squares to R = 0.027 for 3676 unique observed intensities. The X-ray analysis shows that one edge of the Ru₃ triangle is bridged by a hydride and the PHPh ligand, and that the phosphorus-bound hydrogen atom lies over the metal triangle and the phenyl group away from it. This provides an explanation for the ready formation of the capped species H₂Ru₃(CO)₉(PPh) (Va) on pyrolysis of the edge-bridged complex as opposed to the previously reported conversion of HOs₃(CO)₁₀(NHPh) to an orthometallated derivative under similar conditions. An X-ray analysis of H₂Ru₃(CO)₉-(PPh) (Va) confirms the capped geometry. the complex crystallises in the monoclinic space group P2₁/n with a = 9.323(4), b = 15.110(6), c = 45.267(15) Å,β = 91.84(3)°, and Z = 12. the structure was solved and refined using the same techniques as described previously. The final residual R is 0.061 for 4839 reflections. Some reactions of Va show that the phosphorous cap is difficult to displace and stabilises the molecule with respect to decomposition to non-cluster species.