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Fluorotricyanomethane is prepared from potassium tricyanomethanide and perchlorylfluoride. The crystal structure of this compound (orthorhombic, space group P212121, with a=6.270, b=6.734, c=11.776 Å) has been determined by X-ray analysis. The results are discussed in relation to those of (NC)3C? X (X=? CH3, ? Cl, ? Br or ? CN). 相似文献
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Reinhart Ahlrichs 《Chemical physics letters》1975,34(3):570-574
It is shown that HF computations which yield ?i > 0 for an occupied MO do not minimize the HF energy. If ?i > 0, which frequently occurs in the RHF treatment of negative ions, one can reduce ?i to zero and simultaneously lower EHF by an appropriate admixture of a continuum function to the corresponding MO ?. We propose a modification of the HF model that takes these facts into account. Applications to the systems O2?, N3?, C4?, S2?, O22?, C22? are reported and discussed. 相似文献
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Reinhart Ahlrichs 《Theoretical chemistry accounts》1974,33(2):157-167
Methods are described that allow for an efficient evaluation of two-electron integrals over contracted Gaussian lobe functions. The improvement in computational speed is achieved by avoiding the computation of integrals that are: 1. sufficiently small on numerical reasons, 2. zero by symmetry, 3. identical to other integrals by symmetry. Examples of the effectiveness of these techniques are included. We also report the timings for a further processing of two-electron integrals in a Hartree Fock and correlation energy computation. 相似文献
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Ansgar Schäfer Christian Huber Jürgen Gauss Reinhart Ahlrichs 《Theoretical chemistry accounts》1993,87(1-2):29-40
Summary Experimentally known copper selenium clusters show extraordinary geometrical features, especially short Cu-Cu distances. We report the first theoretical investigation of Cu2Se and Cu4Se2. Various quantum chemical methods (SCF, MP2, CPF, CCSD, CCSD(T), LDF) are applied to determine the importance of dynamic electron correlation. We find that inclusion of correlation does not essentially change the electronic structure of the clusters but has a strong influence on geometries. To reduce the computational effort we apply effective core potentials (ECPs) in combination with small, but carefully optimized basis sets. The applicability of simple modellings of correlation energies for approximate inclusion of correlation effects in SCF geometry optimizations is tested. 相似文献
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Reinhart Ahlrichs 《Chemical physics letters》1973,18(4):521-524
Upper bounds are derived for |rμi|, μ = 1,2, ·, where ? denotes an exact electronic bound state wavefunction of a molecular system in the Born-Oppenheimer approximation, and ri is the distance of the ith electron from an appropriately chosen point, e.g., the molecular center. It is further shown that ? decays exponentially if ri → ∞. 相似文献
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Mg(AlH(4))(2) was produced as a nanocrystalline powder by metathesis of NaAlH(4) and MgCl(2). Starting with a structure estimation which was developed from an evaluation of FTIR data and comparison of structural properties of two solvent adducts, quantum chemical calculations were performed on the density functional theory (DFT) level. The calculated atomic positions were used to simulate an X-ray powder diffraction pattern, based on a trigonal unit cell. The simulated pattern was congruent to experimental data. Thus, magnesium alanate exhibits a CdI(2) layer structure, the layers being formed by Mg atoms occupying the Cd sites and AlH(4) tedrahedra occupying the sites of the iodine atoms in CdI(2). 相似文献