We present measurements of the polarized optical spectra of NaV 2 O 5 and LiV 2 O 5 . In an energy range from 0.5 to 5.5 eV, we observe similar peaks in the E a spectra of NaV 2 O 5 and LiV 2 O 5 , which suggests similar electronic structures along the a axis in both materials. On the other hand, we find an almost complete suppression of the peaks in σ b of LiV 2 O 5 around 1 and 5 eV. We attribute this suppression to the charge localization effect originating from the existence of a double-chain charge-ordering pattern in LiV 2 O 5 . : 78.40.-q, 71.35.-y, 75.50.-y In the past several years, quantum phenomena resulting from the low dimensionality of effective electron interactions in solids have been investigated with increasing intensity from both experimental and theoretical points of view. The increase in interest was partially motivated by the discovery of inorganic materials which exhibit quantum effects, such as the
PACS, and by a common belief that these studies would give us a better understanding of electron correlations in general.The vanadate family of AV 2 O 5 oxides have demonstrated a variety of the low-dimensional phenomena which originate from their peculiar crystal structures [3]. These oxides are quasi two-dimensional (2D) materials with layers formed by V O 5 square pyramids. The A atoms are situated between layers as intercalants, but in fact they determine the valence state of vanadium atoms (acting as charge reservoirs). If the A atoms belong to the first column in the periodic table, such as A = Li, Na, each valence electron is shared between two vanadium atoms. As a result the V ions are in a mixed valence-state with an average valence of +4.5. The common consequence of mixed valence in these structures is the appearance of a quasi-1D magnetic interaction, since chains carrying the spin (made of V 4+ , S=1/2) are separated from each other by nonmagnetic chains (V 5+ ). In both LiV 2 O 5 and NaV 2 O 5 the 1D character of the magnetic ordering was confirmed [4,5]. In addition, there is a possibility of the existence of strong valence fluctuations, and eventually charge ordering (CO) effects.
We present a self-consistent quantum-theoretical analysis of the
ground-state energy and low-energy excitation spectrum of a dimerized and
frustrated Heisenberg chain by the bosonization representation in the
continuum-limit approach. The frustration effects on the ground-state energy
and energy gap are investigated for α>αc where α is
the frustration parameter and αc is its critical value, above
which a frustration-induced energy gap is opened. It is shown that as
α increases, the ground-state energy decreases and the energy gap
increases. We find that the dimerization dependence of the ground-state energy and energy
gap for small dimerization obeys the Cross-Fisher power law only
at α = αc, but departs significantly from it when
α>αc. The present results are in good agreement with
numerical analyses from the density-matrix renormalization-group and exact
diagonalization methods. The relevance of our calculated results to recent
experiments on the spin-Peierls compounds CuGeO3 is also discussed.
The use of molybdenum trioxide (MoO 3 ), which is cheap and relatively abundant MoO 3 has been evaluated as a potential alternative to expensive FeMo as a steel alloying method. Pure MoO 3 volatilises very significantly above its melting point (1068 K) and results in a poor alloy yield when added to steel. The volatilisation of MoO 3 in FeSi-MoO 3 , MoO 3 -CaO and MoO 3 -MgO mixtures have been investigated by TG-DTA. Self-reducing experiments of industrial MoO 3 mixed with FeSi, CaO and CaF 2 have been performed in an electric resistance furnace. The results show that the volatilisation of industrial MoO 3 can be effectively inhibited when adding CaO and FeSi and addition of CaF 2 helps form a low melting point slag and results in good separation of metal and slag, The Mo quickly dissolves in the molten steel with 95% recovery.
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