42 research outputs found
Theoretical infra-red, Raman, and Optical spectra of the B36N36 cage
The B36N36 fullerene-like cage structure was proposed as candidate structure
for the single-shell boron-nitride cages observed in electron-beam irradiation
experiment. We have performed all electron density functional calculations,
with large polarized Gaussian basis sets, on the B36N36 cage. We show that the
cage is energetically and vibrationally stable. The infra-red, Raman and
optical spectra are calculated. The predicted spectra, in combination with
experimentally measured spectra, will be useful in conclusive assignment of the
proposed B36N36 cage. The vertical and adiabatic ionization potentials as well
as static dipole polarizability are also reported.Comment: RevTex, 4 pages, 4 figures (TO appear in Physical Review A (Breif
Report)
Incommensurate Transverse Anisotropy Induced by Disorder and Spin-Orbit-Vibron Coupling in Mn12-acetate
It has been shown within density-functional theory that in Mn-acetate
there are effects due to disorder by solvent molecules and a coupling between
vibrational and electronic degrees of freedom. We calculate the in-plane
principal axes of the second-order anisotropy caused by the second effect and
compare them with those of the fourth-order anisotropy due to the first effect.
We find that the two types of the principal axes are not commensurate with each
other, which results in a complete quenching of the tunnel-splitting
oscillation as a function of an applied transverse field.Comment: Will be presented at MMM conference 200
Magnetic ordering, electronic structure and magnetic anisotropy energy in the high-spin Mn single molecule magnet
We report the electronic structure and magnetic ordering of the single
molecule magnet [MnO(2,2'-biphenoxide)Br]
based on first-principles all-electron density-functional calculations. We find
that two of the ten core Mn atoms are coupled antiferromagnetically to the
remaining eight, resulting in a ferrimagnetic ground state with total spin
S=13. The calculated magnetic anisotropy barrier is found to be 9 K in good
agreement with experiment. The presence of the Br anions impact the electronic
structure and therefore the magnetic properties of the 10 Mn atoms. However,
the electric field due to the negative charges has no significant effect on the
magnetic anisotropy.Comment: 4 pages, submitted to PR
Outcomes of the RAFT Trial: Robotic surgery After Focal Therapy
OBJECTIVES: To report toxicity of treatment observed in men participating in the Robotic surgery After Focal Therapy (RAFT) clinical trial. SUBJECTS/PATIENTS AND METHODS: Men were eligible for this prospective single group interventional study if they had histologically confirmed recurrent/residual prostate adenocarcinoma following primary FT. The short-form Expanded Prostate Cancer Index Composite (EPIC-26) measured prior to salvage robotic prostatectomy (S-RARP) and 3-monthly post-operatively together with Clavien-Dindo complications (I-IV). Secondary outcomes included biochemical recurrence-free survival (BCFS) following surgery and need for salvage treatment after surgery. This study is registered with ClinicalTrials.gov NCT03011606. RESULTS: 24 men were recruited between February 2016 and September 2018. 1 patient withdrew from the trial after consenting and before S-RARP. 23 men completed 12-month post S-RARP follow-up. Median EPIC-26 urinary continence scores initially deteriorated after 3 months (82.4 versus 100) but there was no statistically significant difference from baseline at 12 months (100 versus 100, p=0.31). Median lower urinary tract symptom scores improved after 12 months compared to baseline (93.8 versus 87.5, p=0.01). At 12 months, 19/23 (83%) were pad-free and 22/23 (96%) required 0/1 pads. Median sexual function subscale scores deteriorated and remained low at 12 months (22.2 versus 58.3, p<0.001). Utilising a minimally important difference of 9 points, at 12 months after surgery 17/23 (74%) reported urinary continence to be "better" or "not different" to pre-operative baseline. The corresponding figure for sexual function (utilising a minimally important difference of 12 points) was 7/23 (30%). There was no statistically significant difference on median bowel/hormonal subscale scores. Only a single patient had a post-operative complication (Clavien-Dindo Grade I). BCFS at 12 months after surgery was 82.6% (95% confidence interval [CI]: 60.1% - 93.1%] while 4/23 (17%) received salvage radiation. CONCLUSIONS: The RAFT clinical trial suggests toxicity of surgery after FT is low, with good urinary function outcomes, albeit sexual function deteriorated overall. Oncological outcomes at 12 months appear acceptable
Full potential LAPW calculation of electron momentum density and related properties of Li
Electron momentum density and Compton profiles in Lithium along , and directions are calculated using Full-Potential Linear
Augmented Plane Wave basis within generalized gradient approximation. The
profiles have been corrected for correlations with Lam-Platzman formulation
using self-consistent charge density. The first and second derivatives of
Compton profiles are studied to investigate the Fermi surface breaks. Decent
agreement is observed between recent experimental and our calculated values.
Our values for the derivatives are found to be in better agreement with
experiments than earlier theoretical results. Two-photon momentum density and
one- and two-dimensional angular correlation of positron annihilation radiation
are also calculated within the same formalism and including the
electron-positron enhancement factor.Comment: 11 pages, 7 figures TO appear in Physical Review
Predicted Infrared and Raman Spectra for Neutral Ti_8C_12 Isomers
Using a density-functional based algorithm, the full IR and Raman spectra are
calculated for the neutral Ti_8C_12 cluster assuming geometries of Th, Td, D2d
and C3v symmetry. The Th pentagonal dodecahedron is found to be dynamically
unstable. The calculated properties of the relaxed structure having C3v
symmetry are found to be in excellent agreement with experimental gas phase
infrared results, ionization potential and electron affinity measurements.
Consequently, the results presented may be used as a reference for further
experimental characterization using vibrational spectroscopy.Comment: 6 pages, 5 figures. Physical Review A, 2002 (in press
Stability, Electronic Structure and Vibrational Modes of Ti_8C_12 Dimer
We present our density functional results of the geometry, electronic
structure and dissociation energy of Ti_8C_12 dimer. We show that as opposed to
the currently held view that Ti_8C_12 are highly stable monodispersed clusters,
the neutral Ti_8C_12 clusters form covalent bonds and form stable dimers. We
determine that the Ti atoms bond weakly (0.9 eV/bond) to organic ligands such
as ammonia. Alternatively the Met-Car dimer has a cohesive energy of 4.84 eV or
approximately 1.2 eV per bond. While Met-Car dimers are stable, formation of
these dimers may be quenched in an environment that contains a significant
population of organic ligands. The ionization and dissociation energies of the
dimer are of same order which prevents the observation of the dimer in the ion
mass spectroscopy. The analysis of the vibrational frequencies show the
lowest-energy structure to be dynamically stable. We also present infrared
absorption and Raman scattering spectra of the Ti_8C_12 dimer.Comment: 5 pages, 3 figures (Better quality figures available on request).
Physical Review B (Rapid Communication) (2002, in press