19,849 research outputs found
Comparative study between two quantum spin systems KCuCl and TlCuCl
We have performed an {\it ab initio} study of the electronic structure of two
isostructural quantum spin systems, KCuCl and TlCuCl, which have
recently attracted much attention due to their unconventional magnetic
properties. Our first-principles analysis shows unambiguously the role of Tl,
as opposed to structural differences between the two compounds, in making
TlCuCl a {\it strongly} coupled s=1/2 dimer system compared to
KCuCl which shows a {\it weakly} coupled s=1/2 dimer behavior. Good
agreement with the existing analysis of inelastic neutron scattering results
has been observed.Comment: minor changes in text with additional references; in EPL forma
Electronic and magnetic structure of CsVO
We have studied the electronic structure of the spin-gapped system
CsVO by means of an ab initio calculation.
Our analysis and a re-examination of the susceptibility data indicate that
the behavior of this system is much closer to that of an alternating spin-1/2
antiferromagnetic chain with significant inter-dimer coupling and weaker
inter-chain couplings than that of isolated dimers as was initially proposed.
Comparison to the vanadate family members -NaVO,
-LiVO and isostructural compounds like
(VO)PO (VOPO) is discussed.Comment: revised version. To appear in Phys. Rev.
String cosmological model in the presence of a magnetic flux
A Bianchi type I string cosmological model in the presence of a magnetic flux
is investigated. A few plausible assumptions regarding the parametrization of
the cosmic string and magneto-fluid are introduced and some exact analytical
solutions are presented.Comment: 9 pages, 4 Figure
Augmented space recursion for partially disordered systems
Off-stoichiometric alloys exhibit partial disorder, in the sense that only
some of the sublattices of the stoichiometric ordered alloy become disordered.
This paper puts forward a generalization of the augmented space recursion (ASR)
(introduced earlier by one of us (Mookerjee et al 1997(*))) for systems with
many atoms per unit cell. In order to justify the convergence properties of ASR
we have studied the convergence of various moments of local density of states
and other physical quantities like Fermi energy and band energy. We have also
looked at the convergence of the magnetic moment of Ni, which is very sensitive
to numerical approximations towards the k-space value 0.6 with the
number of recursion steps prior to termination.Comment: Latex 2e, 21 Pages, 13 Figures, iopb style file attache
Study of Phase Stability in NiPt Systems
We have studied the problem of phase stability in NiPt alloy system. We have
used the augmented space recursion based on the TB-LMTO as the method for
studying the electronic structure of the alloys. In particular, we have used
the relativistic generalization of our earlier technique. We note that, in
order to predict the proper ground state structures and energetics, in addition
to relativistic effects, we have to take into account charge transfer effects
with precision.Comment: 22 pages, 7 figures. Accepted for publication in JPC
Optical properties of random alloys : Application to Cu_{50}Au_{50} and Ni_{50}Pt_{50}
In an earlier paper [K. K. Saha and A. Mookerjee, Phys. Rev. B 70 (2004) (in
press) or, cond-mat/0403456] we had presented a formulation for the calculation
of the configuration-averaged optical conductivity in random alloys. Our
formulation is based on the augmented-space theorem introduced by one of us [A.
Mookerjee, J. Phys. C: Solid State Phys. 6, 1340 (1973)]. In this communication
we shall combine our formulation with the tight-binding linear muffin-tin
orbitals (TB-LMTO) technique to study the optical conductivities of two alloys
Cu_{50}Au_{50} and Ni_{50}Pt_{50}.Comment: 5 pages, 7 figure
Nonlinear spinor field in cosmology
Within the scope of Bianchi type VI (BVI) model the self-consistent system of
nonlinear spinor and gravitational fields is considered. Exact self-consistent
solutions to the spinor and gravitational field equations are obtained for some
special choice of spatial inhomogeneity and nonlinear spinor term. The role of
inhomogeneity in the evolution of spinor and gravitational field is studied.
Oscillatory mode of expansion of the BVI universe is obtained for some special
choice of spinor field nonlinearity.Comment: RevTex4, 19 pages, 4 figure
Recoil Ranges of Products from Reactions of Cu65 with 11-33 Mev He3 Ions
Recoil ranges of products from reactions copper 65 with 11-35 MeV helium 3 ion
Third-generation muffin-tin orbitals
By the example of sp^3-bonded semiconductors, we illustrate what
3rd-generation muffin-tin orbitals (MTOs) are. We demonstrate that they can be
downfolded to smaller and smaller basis sets: sp^3d^10,sp^3, and bond orbitals.
For isolated bands, it is possible to generate Wannier functions a priori. Also
for bands, which overlap other bands, Wannier-like MTOs can be generated a
priori. Hence, MTOs have a unique capability for providing chemical
understanding.Comment: 13 pages, 8 eps figure
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