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Theoretical study of beryllium borohydride Be(BH₄)₂
Get PDFAb initio calculations using the B3LYP and CCSD(T) methods were employed in this work to explore the most stable structure of the intriguing compound Be(BH₄)₂, for which as many as seven different structures have been proposed in the literature. Use of the B3LYP density functional method with several large basis sets predicts the classic D[subscript 2d] structure to be the lowest energy form, but with a D[subscript 3d] configuration having an energy minimum only 353 cm⁻¹ higher in energy. Potential energy surfaces were calculated using BH₄ torsional and tumbling coordinates and these showed a low energy barrier of 553 cm⁻¹ for interconversion of the two forms. Similar calculations were done using the CCSD(T) method, which is usually considered the "gold standard" of quantum calculations. These were much more time intensive and gave the reverse ordering, with the D[subscript 3d] configuration 90 cm⁻¹ lower in energy than the D[subscript 2d] form. In all cases, inclusion of zero point energy calculated for both isomers tended to lower the ground state energy of the D[subscript 3d] structure relative to that of the D[subscript 2d] form. It is concluded that the D[subscript 3d] structure is the most stable form of Be(BH₄)₂ but that a substantial fraction of the molecules exist in the D[subscript 2d] form in the room temperature vapor.
Recent versions of the Gaussian program used in this work allow calculations of anharmonic properties of a molecule and these were done to predict more accurate vibration-rotation parameters as well as infrared and Raman intensities. These were employed in a reexamination of several earlier experimental infrared spectra. Comparison of the predicted and experimental spectra of Be(BH₄)₂ vapor shows the clear presence of both forms in the room temperature vapor. When Be(BH₄)₂ is isolated in an argon matrix at 20 K, only infrared features attributable to the D[subscript 3d] form remain, a result consistent with the predictions of the CCSD(T) calculations.
Previous infrared spectra of the vapor at 0.0015 cm⁻¹ resolution showed no resolvable vibration-rotation transitions, but concurrent studies in a cold jet revealed many sharp lines with width comparable to the resolution. The jet spectra were quite limited in range however, and efforts to simulate these using theoretical vibration-rotation parameters were unsuccessful. Possible reasons for the extreme congestion of features in both the jet and room temperature spectra are discussed
Interpolating sequences for H∞(BH)
Get PDFWe prove that under the extended Carleson’s condition, a sequence (xn) ⊂ BH is linear interpolating for H∞(BH) for an infinite dimensional Hilbert space H. In particular, we construct the interpolating functions for each sequence and find a bound for the constant of interpolation.The author is supported by Project MTM 2011-22457 (Ministerio de Economía y Competitividad, Spain) and Project P1-1B2014-35 (Universitat Jaume I, Spain
Evaluation and ranking of researchers--Bh Index.
No full textEvaluation and ranking of every author is very crucial as it is widely used to evaluate the performance of the researcher. This article proposes a new method, called Bh-Index, to evaluate the researchers based on the publications and citations. The method is built on h-Index and only the h-core articles are taken into consideration. The method assigns value additions to those articles that receive significantly high citations in comparison to the h-Index of the researcher. It provides a wide range of values for a given h-Index and effective evaluation even for a short period. Use of Bh-Index along with the h-Index gives a powerful tool to evaluate the researchers
ROVIBRATIONAL CHARACTERIZATION OF X BH BY THE EXTRAPOLATION OF PHOTOSELECTED HIGH-RYDBERG SERIES IN BH
No full textAuthor Institution: Department of Chemistry, Purdue University, West Lafayette, IN 47907; Department of Chemistry, University of British Columbia, 6174 University Boulevard,; Vancouver, BC, Canada V6T 1Z3Optical-optical-optical triple resonance spectroscopy of BH isolates high-Rydberg states that form series converging to rotational state specific ionization potentials in the vibrational levels of BH from through . Limits defined by a comprehensive fit of these series to state-detailed thresholds yield rovibrational constants describing the X state of BH. The data provide a first determination of the vibration-rotation interaction parameter cm and a more accurate estimate of cm together with the higher-order anharmonic terms cm and cm. The deperturbation and global fit of series to state-detailed limits also yields a precise value of the adiabatic ionization potential of BH of cm, or eV. High precision is afforded here by the use of graphical analysis techniques, narrow bandwidth laser systems, and an analysis of newly observed, high-principal quantum number Rydberg states that conform well with a Hund's case (d) electron-core coupling limit
More on finite groups with few defining relations
No full textMennicke J, Neumann BH. More on finite groups with few defining relations. Journal of the Australian Mathematical Society. 1989;46(1):132-136.Certain central products of the binary polyhedral groups with finite cyclic groups are here shown to have presentations with two generators and two defining relations; this disproves a conjecture of the second author, stated in J. Austral. Math. Soc. Ser. A 38 (1985), 230–240
COLLISION-INDUCED ELECTRONIC QUENCHING OF
No full textAuthor Institution: Applied Research Corporation; Chemistry Division, Code 6111, Naval Research LaboratoryElectronic quenching cross sections of BH were measured by examining fluorescence decay times in the presence of sixteen collision partners at 298K. The partners exhibit wide variations in mass, electric dipole moment and higher order moments. Except for the extremely low cross sections measured for He and , values range from 5 to . Of the fourteen remaining partners, eleven are represented moderately well by a multipole attractive force model, two (OCS and ) fall well below the expected cross section and one () has an experimental cross section larger than predicted by this model. A temperature comparison is made for the quenching of by CO at 298K and 473K. The measured rate constant at 473K exhibits a 10\% decrease compared to the 298K value with an uncertainty of 11\%
THE REMPI STUDY OF BH IN THE RANGE OF 368-370NM
No full textAuthor Institution: Dept. of Chemistry, Purdue University; Open Laboratory of Bond-Selective Chemistry, University of Science and Technology of ChinaThe mass-selected resonance-enhanced multi-photon ionization (REMPI) of BH in the spectral range of 368-372 nm has been studied. It is shown that the spectral peaks with ion mass 12, 11 and 10 can be assigned to the one-photon transition of 11BH and 10BH free radicals. With very few REMPI studies on BH, the 2-0 band transitions of A-X for 11BH and 10BH are first observed. By using a 40 K rotational temperature and approximately a 600 K background rotational temperature for BH free radicals, the spectra observed was simulated quite well. The observed isotopic shifts of band between 11BH and 10BH, which is between 11.7 and 13.0 cm-1, are mainly due to the vibrational isotope shifts
Device-Aware Test for Back-Hopping Defects in STT-MRAMs
No full textThe development of Spin-transfer torque magnetic RAM (STT-MRAM) mass production requires high-quality dedicated test solutions, for which understanding and modeling of manufacturing defects of the magnetic tunnel junction (MTJ) is crucial. This paper introduces and characterizes a new defect called Back-Hopping (BH); it also provides its fault models and test solutions. The BH defect causes MTJ state to oscillate during write operations, leading to write failures. The characterization of the defect is carried out based on manufactured MTJ devices. Due to the observed non-linear characteristics, the BH defect cannot be modelled with a linear resistance. Hence, device-aware defect modeling is applied by considering the intrinsic physical mechanisms; the model is then calibrated based on measurement data. Thereafter, the fault modeling and analysis is performed based on circuit-level simulations; new fault primitives/models are derived. These accurately describe the way the STT-MRAM behaves in the presence of BH defect. Finally, dedicated march test and a Design-for-Test solutions are proposed.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Computer EngineeringQuantum & Computer Engineerin
Theoretical kinetics analysis for ȮH radical addition to 1,3-butadiene and application to model prediction
No full textThe kinetics of the 1,3-butadiene + ȮH reactions and its impact on combustion kinetic model predictions have been investigated in this work. Geometries and vibrational frequencies for all stationary points were determined at the BH&HLYP/6–311++G(d,p) level of theory, accounting explicitly for the degeneration of torsional motions into hindered rotors. Electronic energies for all stationary points on the related potential energy surface were calculated at the ROCCSD(T)/CBS and G4 levels of theory. Hydroxyl radical addition to the 1,3-butadiene terminal carbon forming allylic hydroxyl radical is the dominant addition entrance channel, while CH2double bondCHCHO+ĊH3 and allyl radical + formaldehyde are the main bimolecular products. A three-membered ring intermediate (IT7) is found to be important in merging pathways originated from terminal and central addition reactions. Pressure and temperature dependent rate constants for ȮH radical addition to 1,3-butadiene are determined integrating the Master Equation on the investigated potential energy surface. Variational transition state theory was used to determine rate constants for the terminal and central addition entrance channels, finding a good agreement with previous experimental measurements. Hydrogen atom abstraction reactions by ȮH radicals from 1,3-butadiene have also been investigated in this work. Rate constants of the important reactions and thermochemistry data for key species calculated in this work were incorporated into AramcoMech3.0 to investigate their influence on the prediction of the reactivity active during 1,3-butadiene oxidation
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