Full-potential LMTO study on the electronic structure of heavy-fermion compound LiV2O4

The electronic structure of heavy fermion compound LiV2O4 has been calculated using a self-consistent full-potential LMTO method. The results show that the conduction bands in this com pound are formed from V 3 d states with a bandwidth of 2.5 eV. The symmetric characteristics of con duction bands are of t2g in principle. The energy gap between conduction bands and fully occupied oxygen 2 p bands is 1.9 eV. The band dispersions near Fermi energy display complicated structures.Furthermore, the N(EF) and γcal are 11.1 (states/eV/f. u. ) and 26.7 mJ/mol@ K2 determined numer ically by LDA calculation, respectively. It is insufficient to clarify the origin of local moment in LiV2O4 from plain LDA calculations. In addition to the above LDA calculation, we also found a LSDA solution of LiV2O4 that is lower in total energy than that of LDA calculation. Similarly, LSDA + GGA calculation yields almost the identical result as that in LSDA. We conclude that the mechanism responsible for heavy fermion properties in LiV2O4 might be somewhat different from the plain Kondo mechanism in conventional 4 f and 5 f heavy fermion compounds and perhaps the quantum transition might play an adequate role in heavy-fermion behaviors in LiV2O4.     

Synthesis and characterization of C3N4 hard films

C₃N₄ films have been synthesized on both Si and Ft substrates by microwave plasma chemical vapor deposition (MPCVD) method. X-ray spectra were calculated for single phase α-C₃N₄ and β-C₃N₄ respectively. The experimental X-ray spectra of films deposited on both Si and Pt substrates showed all the strong peaks of α-C₃N₄ and β-C₃N₄ so the films are mixtures of α-C₃N₄ and β-C₃N₄. The N/C atomic ratio is in the range of 1.0–2.0. X-ray photoelectron spectroscopy (XPS) analysis indicated that the binding energy of Is and N ls are 286.2 eV and 399.5 eV respectively, corresponding to polarized C-N bond. Fourier transform infrared absorption (FT-IR) and Raman spectra support the existence of C-N covalent bond in the films. Nano-indentation hardness tests showed that the bulk modulus of a film deposited on Pt is up to 349 GPa     

Phase transition in layered perovskite-like manganate Ca3Mn2O7 under high pressure

In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca₃Mn₂O₇ powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca₃Mn₂O₇ is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca₃Mn₂O₇ underwent two phase transitions under pressures in the range of 0–35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.     

X-Ray spectroscopic evidence for chemical bonding in manganese selenide (MnSe)

K absorption spectra of manganese and selenium have been recorded photographically in the pure metals and in the intermetallic compound manganese selenide (MnSe), employing a bent crystal X-ray spectrograph. It has been observed that the Mn K absorption discontinuity in MnSe shifts by 5·6 eV toward the high energy side with respect to the discontinuity in the pure metal. On the other hand, the Se K edge in MnSe is found to shift by 3·4 eV toward the low energy side with respect to the discontinuity in pure selenium. Also, emission work has revealed that the Mn K_β5 band in the compound shifts by about 5 eV toward the high energy side with respect to that in the pure metal. It has been shown that these results confirm the resonatingp ³ type of chemical bonding in the compound, as suggested theoretically by Pearson.     

X-ray spectroscopic study of chemical bonding in NiSe and NiSe2

The K absorption spectra of nickel and selenium have been recorded photographically in the pure metals and the compounds NiSe and NiSe₂. It has been observed that the Ni discontinuity shifts toward the high energy side with respect to that in the pure metal by about 5.0 eV for NiSe and about 6.7 eV for NiSe₂. The Se edge in both these compounds is found to shift by about 2.6 eV toward the low energy side with respect to that in pure selenium. From these results it is possible to obtain the bonding pictures for the compounds. The compound NiSe appears to have resonating p³ type of bonding. For NiSe₂ the orbitals involved in the bonding are d²sp³ for the metal atom and sp³ for the metalloid atom. The electrical behaviour of the compounds has been explained on the basis of these bonding pictures.     

Anomalous nonconservation of baryon number in decays of heavy fermions in electroweak theory

It is shown that the inclusion of a heavy fermionic doublet in the standard model of electroweak interactions can lead to the formation of nontopological soliton states of two different types. The effects of the complicated vacuum structure lead to instability of the soliton states with respect to anomalous decay with nonconservation of the fermionic quantum numbers. If the fermion mass exceeds a critical value m_cr10–18 TeV, then, besides the formation of the soliton state, there exists a possibility of rapid anomalous decay of the bare fermion.Institute of Nuclear Physics, USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 90, No. 1, pp. 21–36, January, 1992.     

The region of values of the system { f ( z 1),..., f ( z n )} in the class of typically real functions. III

The paper studies the region of values D_m,n(T) of the system {f(z₁), f(z₂),..., f(z_m), f(r₁), f(r₂),..., f(r_n)}, where m ≥ 1; n > 1; z_j, j = 1, ... m, are arbitrary fixed points of the disk U = {z: |z| < 1} with Im z_j ≠ 0, j = 1, 2, ..., m; r_j, 0 < r_j < 1, j = 1, 2, ..., n, are fixed; f ∈ T, and the class T consists of functions f(z) = z + c₂z² + ... regular in the disk U and satisfying the condition Im f(z) · Im z > 0 for Im z ≠= 0, z ∈ U. An algebraic characterization of the set D_m,n(T) in terms of nonnegative-definite Hermitian forms is provided, and all the boundary functions are described. As an implication, the region of values of f(z₁) in the subclass of functions f ∈ T with prescribed values f(r_j) (j = 1, 2, 3) is determined. Bibliography: 12 titles. Dedicated to the 100th anniversary of my father’s birthday __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 337, 2006, pp. 23–34.     

Fully-angular polyhex chains with minimal total π-electron energy

By Hückel molecular orbital (HMO) theory, the calculation of the total energy of all π-electrons in conjugated hydrocarbons can be reduced to that of E(G)=|λ₁|+|λ₂|+?+|λn|, where λi are the eigenvalues of the corresponding graph G. Denote by Ψn the set of all fully-angular polyhex chains with n hexagons. In this paper, we show that Hn has the minimum total π-electron energy among chains in Ψn, where Hn is the helicene chain.     

The validity of the strong perfect-graph conjecture for (K4−e)-free graphs

Berge's strong perfect-graph conjecture states that a graph is perfect iff it has neither C_2n+1 nor $\text{C}{}_{\mathrm{2n+1}}$, n ≥ 2 as an induced subgraph. In this note we establish the validity of this conjecture for (K₄?e)-free graphs.     

Universal embeddings for theD4(2) hexagon andJ2near-octagon

The universal embeddings overF₂ of the generalized hexagon for³D₄(2)and the near-octagon forJ₂are determined to be the 28-dimensional adjoint modules: for typeD₄in the first case, and in the second from the 14-dimensional adjointF₄-module forG₂(4)containingJ₂.     

数域中tame 核的p-秩

Let E/F be a Galois extension of number fields with Galois group G=Gal(E/F), and let p be a prime not dividing #G. In this paper, using character theory of finite groups, we obtain the upper bound of #K₂O_E if the group K₂O_E is cyclic, and prove some results on the divisibility of the p-rank of the tame kernel K₂O_E, where E/F is not necessarily abelian. In particular, in the case of G=C_n, D_n, A₄, we easily get some results on the divisibility of the p-rank of the tame kernel K₂O_E by the character table. Let E/Q be a normal extension with Galois group D_l, where l is an odd prime, and F/Q a non-normal subextension with degree l. As an application, we show that f|p-rank K₂O_F, where f is the smallest positive integer such that p^f≡±1(mod l).     

The kernel of the Rost invariant, Serre''s Conjecture II and the Hasse principle for quasi-split groups 3,6 D 4 , E 6 , E 7

 We prove that for a simple simply connected quasi-split group of type ^3,6 D ₄ ,E ₆ ,E ₇ defined over a perfect field F of characteristic ≠=2,3 the Rost invariant has trivial kernel. In certain cases we give a formula for the Rost invariant. It follows immediately from the result above that if cd F≤2 (resp. vcd F≤2) then Serre's Conjecture II (resp. the Hasse principle) holds for such a group. For a (C ₂ )-field, in particular ℂ(x,y), we prove the stronger result that Serre's Conjecture II holds for all (not necessary quasi-split) exceptional groups of type ^3,6 D ₄ ,E ₆ ,E ₇ . Received: 27 March 2002 / Published online: 28 March 2003 The author gratefully acknowledge the support of TMR ERB FMRX CT-97-0107 and Forschungsinstitut für Mathematik, ETH in Zürich     

M0(G)-boundaries are M(G)-boundaries

Let M(G) denote the convolution algebra of finite regular complex-valued Borel measures on a locally compact abelian group G, and let M₀(G) be the ideal consisting of those measures whose Fourier-Stieltjes transforms vanish at infinity. Then there is a natural inclusion of the maximal ideal space Δ₀ of M₀(G) in the maximal ideal space of M(G). The main result states that any subset of Δ₀ which is a boundary for M₀(G) is a boundary for M(G). An immediate corollary is that the ?ilov boundary of M₀(G) is dense in the ?ilov boundary of M(G).     

Adams谱序列上的非平凡乘积b_0k_0δ_(s+4)

主要用May谱序列证明了非平凡的乘积b_0k_0δ_(s+4)∈Ext_A~(s+8,t)(Z_p,Z_p),其中p是大于等于7的素数,0≤sp-4,q=2(p-1),t=(s+4)p~3q+(s+3)p~2q+(s+5)pq+(s+2)q+s.     

On Two-Graphs of Ovoids inO2n+ 1(q)

Moorhouse and Gunawardena [1] have shown that if the avoids in finite orthogonal spaces of typeO_{2n + 1}(q),qodd, exist then their two-graphs are regular. In this note, we present a new geometrical proof for the regularity of those two-graphs.     

Preparation and optical properties of GaSb nanoparticles embedded in SiO2 composite films

The composite films of GaSb nanoparticles embedded in SiO₂ matrices were fabricated by radio-frequency magnetron co-sputtering. Transmission electron microscope and X-ray diffraction pattern indicate that the GaSb nanoparticles were uniformly dispersed in SiO₂ matrices. Room temperature transmission spectra exhibit a blue shift of about 2.73 eV. The blue shift increases with decreasing size of GaSb nanoparticles, suggesting the existence of quantum size effects. Room temperature Raman spectra show that there is a larger Raman peak red shift and broadening of the composite films than that of bulk GaSb. This phenomenon is explained by photon confinement effect and tensile stress effect     

Numerical study of heat transfer enhancement in mixed convection flow along a vertical plate with heat source/sink utilizing nanofluids

Steady, mixed convection laminar boundary layer flow of incompressible nanofluid along the vertical plate with temperature dependent heat source/sink has been investigated numerically. The resulting non-linear governing equations (obtained with the Boussinesq approximation) are solved, using a robust, extensively validated, variational finite element method (FEM) for both spherical and cylindrical shaped nanoparticles with volume fraction ranging up to 4%, with associated boundary conditions and the effect of the parameters governing the problem are discussed. Different water-based nanofluids containing Cu, Ag, CuO, Al₂O₃, and TiO₂ are taken into consideration. The results show that the average Nusselt number is found to decrease for Ag, Cu, CuO, Al₂O₃, and TiO₂. The present study is of immediate interest in next-generation solar film collectors, heat exchangers technology, materials processing exploiting vertical surfaces, geothermal energy storage and all those processes which are highly affected with heat enhancement concept.     

Augmenting Edge-Connectivity over the Entire Range inÕ(nm) Time

For a given undirected graphG = (V, E, c_G) with edges weighted by nonnegative realsc_G:E → R ⁺ , let Λ_G(k) stand for the minimum amount of weights which needs to be added to makeG k-edge-connected, and letG*(k) be the resulting graph obtained fromG. This paper first shows that function Λ_Gover the entire rangek [0, +∞] can be computed inO(nm + n² log n) time, and then shows that allG*(k) in the entire range can be obtained fromO(n log n) weighted cycles, and such cycles can be computed inO(nm + n² log n) time, wherenandmare the numbers of vertices and edges, respectively.     

Mechanical properties of irradiated silicone compounds

The change in the mechanical properties of silicone compounds subjected to irradiation with electrons and x rays has been investigated. The compounds contained the fillers ZnO and SiO₂ and, moreover, Be₂O₃ and Fe₂O₃. It is shown that as a result of prolonged irradiation the capacity of the compounds for high elastic deformation is reduced by a factor of 5–6, the true strength values are reduced by a factor of 2–3, and the stiffness of the compounds increases by a factor of 2–3. The compound containing Be₂O₃ proved to be the more radiation-resistant material.Institute of the Chemical Industry, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 610–615, July–August, 1973.     

Quantization of orbit bundles in \mathfrakg\mathfrakln* (\mathbbC) \mathfrak{g}\mathfrak{l}_n^* (\mathbb{C})

Let G be the complex general linear group and its Lie algebra equipped with a factorizable Lie bialgebra structure; let U_ħ() be the corresponding quantum group. We construct explicit U_ħ()-equivariant quantization of Poisson orbit bundles O _λ → O _μ in *.