Analytical infrared intensities for periodic systems with local basis sets

We report a method for the efficient evaluation of analytic infrared (IR) intensities within generalized Kohn-Sham density functional theory using Gaussian orbitals and periodic boundary conditions. A discretized form of the Berry phase is used to evaluate a periodic dipole moment and its derivatives with respect to in-phase nuclear coordinate displacements. Benchmark calculations are presented for one-dimensional chains of water molecules and poly(paraphenylenevinylene).Comment: 16 pages, 3 figures, 4 tables, submitted to Phys. Rev.

Phonon Properties of Knbo3 and Ktao3 from First-Principles Calculations

The frequencies of transverse-optical $\Gamma$ phonons in KNbO$_3$ and KTaO$_3$ are calculated in the frozen-phonon scheme making use of the full-potential linearized muffin-tin orbital method. The calculated frequencies in the cubic phase of KNbO$_3$ and in the tetragonal ferroelectric phase are in good agreement with experimental data. For KTaO$_3$, the effect of lattice volume was found to be substantial on the frequency of the soft mode, but rather small on the relative displacement patterns of atoms in all three modes of the $T_{1u}$ symmetry. The TO frequencies in KTaO$_3$ are found to be of the order of, but somehow higher than, the corresponding frequencies in cubic KNbO$_3$.Comment: 8 pages + 1 LaTeX figure, Revtex 3.0, SISSA-CM-94-00

The vibrational spectrum of CaCO3 aragonite: A combined experimental and quantum-mechanical investigation

The vibrational properties of CaCO3 aragonite have been investigated both theoretically, by using a quantum mechanical approach (all electron Gaussian type basis set and B3LYP HF-DFT hybrid functional, as implemented in the CRYSTAL code) and experimentally, by collecting polarized infrared (IR) reflectance and Raman spectra. The combined use of theory and experiment permits on the one hand to analyze the many subtle features of the measured spectra, on the other hand to evidentiate limits and deficiencies of both approaches. The full set of TO and LO IR active modes, their intensities, the dielectric tensor (in its static and high frequency components), and the optical indices have been determined, as well as the Raman frequencies. Tools such as isotopic substitution and graphical animation of the modes are available, that complement the analysis of the spectrum

Efficacy of five ‘sporicidal’ surface disinfectants against Clostridioides difficile spores in suspension tests and 4-field tests

Background: A sporicidal surface disinfection is recommended both for the outbreak and the endemic setting but a comparative evaluation on the efficacy of ‘sporicidal’ surface disinfectants using suspension tests and 4-field tests has not been performed. Aim: To determine the efficacy of five ‘sporicidal’ surface disinfectants (three ready-to-use wipes (A, B, E), two concentrates (C, D) based on peroxides or aldehydes against C. difficile spores. Methods: The efficacy was determined under clean conditions using a suspension test and the 4-field test. Each test was performed in duplicate in two separate laboratories. Wipes were wrung to collect the solution for the suspension tests. Results: Product A (peracetic acid; 5 min), product C (peracetic acid; 2% solution in 15 min or 1% solution in 30 min) and product D (peracetic acid; only 2% solution in 15 min) were effective with at least a 4 log10-reduction of C. difficile spores in suspension and on surfaces. Product B (hydrogen peroxide) was not effective in suspension (0.9 log10 after 15 min; 3.2 log10 after 1 h) and on surfaces (2.8 log10 after 15 and 60 min). Product E based on glutaraldehyde, (ethylendioxy)dimethanol and DDAC demonstrated 0.9 log10 after 4 h in suspension and 4.5 log10 after 4 h on surfaces. Conclusions: Not all surface disinfectants with a sporicidal claim were effective against C. difficile spores in standardized suspension tests and in the 4-field test. In clinical practice preference should be given to products that reliably pass the efficacy criteria of both types of tests.Peer Reviewe

Erratum: Force constants of the metaborate ion in alkali halides

Erratum for the article: Decius, J. C. ; Becker, Charles R. ; Fredericks, W. J. : Force constants of the metaborate ion in alkali halides, In: THE JOURNAL OF CHEMICAL PHYSICS (1972), 56, 10, 5189-5190.Hierbei handelt es sich um eine Korrektur zum Artikel: Decius, J. C. ; Becker, Charles R. ; Fredericks, W. J. : Force constants of the metaborate ion in alkali halides, In: THE JOURNAL OF CHEMICAL PHYSICS (1972), 56, 10, 5189-5190

CO BOND MOMENT IN THE CARBONATE ION

Author Institution: Department of Chemistry, Oregon State CollegeVaritation of the $C^{12} - C^{13}$ ratio in carbonates of the aragonite lattice leads to fine structure in the 12$\mu$ region whose spacing and qualitative intensity can be fitted satisfactorily by the introduction of a nearest neighbor coupling constant in the potential energy. The coupling constant is believed to arise from dipole-dipole forces. From the coupling constant the value of the CO bond moment is found to be $1.52 \pm 0.1$ debyes in $BaCO_{3}$, $1.56 \pm 0.1$ debyes in $SrCO_{3}$. The coupling is so large in $CaCO_{3}$ (on account of the inverse cube dependence upon interdipole distance) that the perturbation theory cannot be applied without modification

Force constants of the metaborate ion in alkali halides

No abstract availabl

EFFECT OF NITROGEN ISOTOPES ON THE PERPENDICULAR BENDING MODE OF NITRATE ION

Author Institution: Department of Chemistry, Oregon State CollegeThe Infrared absorption of Nujol mulls of $KNO_{3}$ and of $Ba(NO_{3})_{2}$ has been studied in the vicinity of 12. Solid solutions of varying $N^{14}$ - $N^{15}$ ratio were prepared by dissolving mixtures of $KNO_{3}$ containing a nominal 62% $N^{15}$ with ordinary $KNO_{3}$ in a minimum amount of water. The salt was recrystallized by sudden addition of a large excess of chilled ethanol. At least two components of the absorption have been identified in both the $N^{14}$ region (825 to $835 cm^{-1}$) and in the $N^{15}$ region (806 to $811 cm^{-1}$). In $Ba(NO_{3})_{2}$, on the contrary, only a single peak appears in each region. Potassium nitrate exists in the aragonite structure at room temperature; barium nitrate is similar crystallographically to fluorite. Since the $KNO_{3}$ structure is favorable for the existence of a relatively large dipole-dipole interaction between nearest $NO_{3}^{-}$ neighbors whereas the $Ba(NO_{3})_{2}$ structure is not, the results are interpreted as a dipole-dipole coupling. These results also indicate that isotopic abundance can be measured much more conveniently using barium nitrate

Relaxation Times for Vibrational Absorption

Author Institution: Oregon State CollegePresentations without an abstract printed in the proceedings do not have an abstract (image or text) in the Knowledge Bank record