共查询到7条相似文献,搜索用时 15 毫秒
1.
Ab initio MO calculations are performed on a series of ion-molecular and ion pair-molecular complexes of H2O + MX (MX = LiF, LiCl, NaCl, BeO and MgO) systems. BSSE-corrected stabilization energies, optimized geometrical parameters,
internal force constants and harmonic vibrational frequencies have been evaluated for all the structures of interest. The
trends observed in the geometrical parameters and other properties calculated for the mono-hydrated contact ion pair complexes
parallel those computed for the complexes of the individual ions. The bifurcated structures are found to be saddle points
with an imaginary frequency corresponding to the rocking mode of water molecules. The solventshared ion pair complexes have
high interaction energies. Trends in the internal force constant and harmonic frequency values are discussed in terms of ion-molecular
and ion-pair molecular interactions. 相似文献
2.
Based on first-principles total energy calculations, we have investigated the systematic trends for structural, electronic and elastic properties of the MAX phases M2GaN depending on the type of M transition metal (M are Ti, V and Cr). The optimized zero pressure geometrical parameters: the two unit cell lengths (a, c), the internal coordinate z and the bulk modulus are calculated. The results for the lattice constants are in agreement with the available experimental data. The band structures show that all studied materials are electrical conductors. The analysis of the site-projected l-decomposed density of states shows that bonding is due to M d-N p and M d-Ga p hybridizations. The elastic constants are calculated using the static finite strain technique. The shear modulus C44, which is directly related to the hardness, reaches its maximum when the valence electron concentration is in the range 10.5–11.0. The isotropic elastic moduli, namely, bulk modulus (B), shear modulus (G), Young's modulus (E) and Poisson's ratio (σ) are calculated in framework of the Voigt–Reuss–Hill approximation for ideal polycrystalline M2GaN aggregates. We estimated the Debye temperature of M2GaN from the average sound velocity. This is the first quantitative theoretical prediction of the electronic structures, and elastic constants and related properties for Ti2GaN, V2GaN and Cr2GaN compounds that require experimental confirmation. 相似文献
3.
The structural and electronic properties of anode materials LiMN (M = Ni, Co, Cu) for lithium ion batteries have been studied by the first-principles method. The calculations reveal different bonding characteristics for LiMN (M = Ni, Co, Cu). The Li–N bond on the LiN planes shows covalent mixed with ionic characters, with the covalent interaction strengthened and ionic one weakened gradually from LiNiN to LiCoN and then to LiCuN. In the direction of N–M chains, the bonding characteristics are analogous on the whole. The N–M bonding shows both ionic and covalent characters again, while the covalent interaction slightly weakened in sequence. Electronic structure calculations suggest that LiMN (M = Ni, Co, Cu) are all metallic, where the LiNiN is of anisotropic conductivity along the directions of N–Ni chains, while for LiCoN and LiCuN, electrons can also be feebly conductive on the LiN planes besides along the linear N–Co and N–Cu chains. 相似文献
4.
Rohini Mani Keka R. Chakraborty Joby E. Joy J. Gopalakrishnan A.K. Tyagi 《Journal of solid state chemistry》2010,183(6):1380-1387
We describe an investigation of the structure and dielectric properties of MM′O4 and MTiM′O6 rutile-type oxides for M=Cr, Fe, Ga and M′=Nb, Ta and Sb. All the oxides adopt a disordered rutile structure (P42/mnm) at ambient temperature. A partial ordered trirutile-type structure is confirmed for FeTaO4 from the low temperature (17 K) neutron diffraction studies. While both the MM′O4 oxides (CrTaO4 and FeTaO4) investigated show a normal dielectric property MTiM′O6 oxides for M=Fe, Cr and M′=Nb/Ta/Sb display a distinct relaxor/relaxor-like response. Significantly the corresponding gallium analogs, GaTiNbO6 and GaTiTaO6, do not show a relaxor response at T<500 K. 相似文献
5.
Marine ReynaudPrabeer Barpanda Gwenaëlle RousseJean-Noël Chotard Brent C. MelotNadir Recham Jean-Marie Tarascon 《Solid State Sciences》2012,14(1):15-20
Our work in metal fluorosulphate chemistry, which was triggered by the discovery of the tavorite-phase of LiFeSO4F, has unveiled many novel Li- and Na-based phases with desirable electrochemical and/or transport properties. Further exploring this rich crystal chemistry, we have synthesized the Na-based magnesium, copper and zinc fluorosulphates, which crystallise in the maxwellite (tavorite-like framework) structure just as their Fe and Co counterparts, which were previously reported. These phases show ionic conductivities in the range of ∼10−7 S cm−1 or ∼10−11 S cm−1 depending upon their synthesis process and no reversible electrochemical activity versus Na. 相似文献
6.
7.
Ab initio calculations with full electron correlation by the perturbation method to second order and hybrid density functional theory calculations by the B3LYP method utilizing the 6-31G(d), 6-311+G(d, p), and 6-311+G(2d, 2p) basis sets have been carried out for the XNCO and XOCN (X = H, F, Cl, Br) molecules. From these calculations, force constants, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios, and structural parameters have been determined and compared to the experimental quantities when available. By combining previously reported rotational constants for HNCO, ClNCO and BrNCO with the ab initio MP2/6-311+G(d, p) predicted structural values, adjusted r0 parameters have been obtained. The r0 values for BrNCO are: r(BrN) = 1.857(5); r(NC) = 1.228(5); r(CO) = 1.161(5) Å; BrNC = 117.5(5) and NCO = 172.3(5)°. For ClNCO the determined r0 parameters are in excellent agreement with the previously determine rs values, whereas those for HNCO the HNC angle is larger with a value of 126.3(5)° compared to the previous reported value of 123.9(17)°. However, considering the relatively large uncertainty in the value given initially the two results are in near agreement. Structural parameters are also estimated for FNCO and XOCN (X = H, F, Cl, Br). The centrifugal distortion constants have been calculated and are compared to the experimentally (XNCO: X = H, Cl, Br) determined values. Predicted values for the barriers of linearity are given for both the XNCO (X = H, F, Cl, Br) molecules and the results were compared to the corresponding isothiocyanate molecules. The predicted frequencies for the fundamentals of the XNCO molecules compare favorably to the experimental values but some of the predicted intensities differ significantly from those in the observed spectra. The two OCN bends for HOCN have been assigned and the frequencies for the two corresponding fundamentals of DOCN are predicted. 相似文献