20,472 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.
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
Comparative study of FeCr2S4 and FeSc2S4: Spinels with orbitally active A site
Using first-principles density functional calculations, we perform a
comparative study of two Fe based spinel compounds, FeCr2S4 and FeSc2S4. Though
both systems contain an orbitally active A site with an Fe2+ ion, their
properties are rather dissimilar. Our study unravels the microscopic origin of
their behavior driven by the differences in hybridization of Fe d states with
Cr/Sc d states and S p states in the two cases. This leads to important
differences in the nature of the magnetic exchanges as well as the nearest
versus next nearest neighbor exchange parameter ratios, resulting into
significant frustration effects in FeSc2S4 which are absent in FeCr2S4.Comment: 5 pages, 4 figures Phys Rev B (rapid commun) to appear (2010
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
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
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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