Increasingly, there is concern that the environment for conducting excellent research is deteriorating within the United States' large public research laboratories. This worry is being voiced both by the rank and file scientists within these institutions, as well as by leaders responsible for stewarding the US research infrastructure. The article describes a study which is limited to assessing the...

This paper presents initial work at two U.S. Department of Energy (DOE) national laboratories to develop a process for assessing and improving the effectiveness of research organizations. The approach to assessment reflects the complexity of the research environment and provides information that allows the research organization to define a few key actions for improvement. The work described here focuses on identifying attributes of DOE laboratory research environments that are most important for fostering excellent research. Thirty-six attributes in four areas were identified by scientists and engineers at these institutions and are presented using the Competing Values model for discussing organizational effectiveness. These attributes served as the basis for the development of a self-assessment survey and improvement process designed specifically for research environments. Assessments involving more than 1000 scientists and engineers in four organizations have shown that this approach provides a good basis for understanding and improvement.

Dehydroxylated silica exhibits two well-defined infrared bands at 888 and 907 cm−1 previously assigned to a highly reactive strained surface defect. Comparisons of the spectra of dehydroxylated silica to frequencies and intensities calculated using molecular orbital (MO) calculations and to spectra obtained for cyclodisiloxanes suggest that the strained surface defect consists of an edge-shared silicate tetrahedral ring. Changes in vibrational frequencies and peak intensities with 18O labeling for both the surface defect and the cyclodisiloxanes are consistent with those expected for ring vibrational modes. The IR bands associated with the strained edge-shared ring disappear when either the surface defects or the cyclodisiloxanes react with water. Reactions of the surface defect can be used to study how strain enhances the reactivity of Si-O-Si bonds for modeling phenomena such as stress corrosion cracking.

The mechanism of decomposition of nitramines has been studied theoretically using the quantum chemical Bond-Additivity-Corrected Møller-Plesset fourth order pertrubation theory method (BAC-MP4). The BAC-MP4 method is used to calculate the heats of formation and free energies of the nitramines H2NNO2 and CH3NHNO2 as well as of the molecular radical species which might arise from the decomposition process. The thermochemical properties of transition state activated complexes have also been calculated. The bond energies and dissociation energies obtained from these calculations are used to determine decomposition pathways of propellant nitramines such as HMX and RDX. The results indicate that at high temperatures, bond fission of the nitro group (with a bond energy of ≈200 kJ-mol−1) should play an important role as the initial decomposition step. At lower temperatures, the five-centered HONO elimination with a dissociation energy of ∼170 kj-mol−1 is possible but has a small preexponential factor compared to experimental decomposition rates. We propose a new decomposition mechanism, involving attack by autocatalytic generated H atoms, which provides a lower energy pathway (∼128 kJ-mol−1) which can form nitrosamines as intermediate products leading to N2O formation. The H atom attack can also lead to HCN and NO2 formation through pathways analogous to the initial N−NO2 bond breaking process.

ADVERTISEMENT RETURN TO ISSUEArticleNEXTDimerization energy of boraneMichael. Page, George F. Adams, J. Stephen. Binkley, and Carl F. MeliusCite this: J. Phys. Chem. 1987, 91, 11, 2675–2678Publication Date (Print):May 1, 1987Publication History Published online1 May 2002Published inissue 1 May 1987https://pubs.acs.org/doi/10.1021/j100295a001https://doi.org/10.1021/j100295a001research-articleACS PublicationsRequest reuse permissionsArticle Views261Altmetric-Citations37LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Accurate ab initio calculations are performed to study the structures and energies of small carbon clusters (Cn, n=2–10). The effects of polarization functions and electron correlation are included in these calculations. Significant odd–even alternation is found in the nature of the cluster geometries with the odd-numbered clusters having linear structures and many of the even-numbered clusters preferring cyclic structures. Energetically, odd-numbered clusters (up to C7) are found to be more stable than the adjacent even-numbered clusters. Ionization potentials are calculated and used in conjunction with the cluster energies to explain the fragmentation behavior of small carbon cluster ions.

The interaction energy of two HF molecules at 1332 individual points has been calculated with Moeller–Plesset (many–body) perturbation theory at the MP4-SDTQ level using a 6-311G** basis set. 293 of the points correspond to stretching of one HF molecule from its equilibrium geometry. No attempt was made to use a sufficiently fine grid to accurately describe the well region corresponding to hydrogen bonding. However, the location and minimum energy are consistent with experiment and other accurate theoretical results. An extensive global fit (rms error of 1 kcal/mol) is reported of 1319 points (below 10 eV of potential energy) using a modified London potential with corrections obtained using polynomials through four-body interactions. A model electrostatic potential represents the long-range interaction. In addition, the use of an expansion in products of three Legendre functions is discussed. It is shown that the latter approach, although accurately fitting the ab initio data, has difficulties interpolating in regions of the surface exhibiting diverse magnitudes of potential energy, and therefore must be used with caution. This surface should be useful for studies of T–V–R processes in this system.

In order to provide ab initio wave functions for the evaluation of intra- and interatomic Auger rates in the NaF crystal, new open-shell restricted Hartree-Fock calculations have been performed for several ${\mathrm{Na}}^{+}$ hole states of an (${\mathrm{NaF}}_{6}$${)}^{5\mathrm{\ensuremath{-}}}$ cluster embedded in a cubic array of point ions. The basis sets are described and the self-consistent-field ionization energies \ensuremath{\Delta}${E}_{\mathrm{SCF}}$ are compared with values available from the literature. It is noted that appreciable valence electron charge is transferred between the F and Na atoms upon Na hole creation.

The preferred structures and dissociation energies of Be4 and Be13 are determined by ab initio methods, including Møller-Plesset perturbation theory, coupled-cluster theory, and multireference CI. Both species serve as calibration points for basis set extension and electron correlation effects. The results are used to interpret binding energies for larger Be clusters obtained only at the SCF level with smaller basis sets.

Ab initio molecular orbital theory is used to determine if the molecular ion HOC+ is linear (as are the isoelectronic species HCN, HNC, HCO+, etc.), or if it is quasilinear. Near the Hartree-Fock limit the molecule is either linear, or very close to linear. Electron correlation favors the linear geometry, leading to the unequivocal prediction of a linear molecule. Detailed comparisons between HOC+ and isoelectronic HNC show an apparent lack of convergence in the bending potential for the former which is remedied by the addition of f functions to the basis set. The HOC+ potential energy surface is computed in the bending and bend-stretch coordinates and fit to an analytical function. Use of this function to compute the rotation-vibration energies results in improved agreement with experiment relative to previous potentials by nearly two orders of magnitude, as documented in the accompanying paper.

For many years it has been recognized that fundamental physical constraints such as the speed of light will limit the ultimate speed of single processor computers to less than about three billion floating point operations per second (3 GFLOPS). This limitation is becoming increasingly restrictive as commercially available machines are now within an order of magnitude of this asymptotic limit. A natural way to avoid this limit is to harness together many processors to work on a single computational problem. In principle, these parallel processing computers have speeds limited only by the number of processors one chooses to acquire. The usefulness of potentially unlimited processing speed to a computationally intensive field such as quantum chemistry is obvious. If these methods are to be applied to significantly larger chemical systems, parallel schemes will have to be employed. For this reason we have developed distributed-memory algorithms for a number of standard quantum chemical methods. We are currently implementing these on a 32 processor Intel hypercube. In this paper we present our algorithm and benchmark results for one of the bottleneck steps in quantum chemical calculations: the four index integral transformation.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermal decomposition of silaneMark S. Gordon, David R. Gano, J. Stephen. Binkley, and Michael J. FrischCite this: J. Am. Chem. Soc. 1986, 108, 9, 2191–2195Publication Date (Print):April 1, 1986Publication History Published online1 May 2002Published inissue 1 April 1986https://pubs.acs.org/doi/10.1021/ja00269a011https://doi.org/10.1021/ja00269a011research-articleACS PublicationsRequest reuse permissionsArticle Views824Altmetric-Citations83LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The equilibrium geometry, harmonic vibrational frequencies, and infrared intensities of the intramolecularly hydrogen-bonded malonaldehyde molecule are shifted abruptly by the effects of electron correlation. The present ab initio study employed second-order perturbation theory in conjunction with a 6–31G★★ basis set of contracted Gaussian functions. Comparison with the two experimental infrared assignments of Smith, Wilson and Duerst is made.

The structures and binding energies of the complexes (H2O)2, (H2O)2H+, (HF)2, (HF)2H+, F2H−, and (NH3)2 have been examined using much higher levels of theory than has been previously applied to these systems. These methods including large basis sets and full optimization of structures with the effects of electron correlation included, are known to give single bond energies to an accuracy of about 2 kcal mol−1 and are found in this study to give excellent agreement with the extensive experimental data available for the hydrogen fluoride and water dimers. The Cs open form of ammonia dimer remains a very shallow minimum energy structure at these levels, in agreement with previous theoretical results but seemingly in disagreement with experiment. The theoretical enthalpy of association of H5O+2 is found to be −35.0 kcal mol−1, in slight disagreement with the most recent experimental results, but in accord with earlier ones, which suggests that these experiments should be reexamined. The enthalpy of association of H2F+ is predicted to be −33.5 kcal mol−1, and that of F− with HF to be −46.4 kcal mol−1. A study of the effects of basis set expansion on the structure of the water dimer shows that the structure is much more sensitive to basis set at the Hartree–Fock level than when correlation is included. A valence triple-zeta basis plus two sets of first polarization functions and one set of diffuse functions appears to be necessary to approach the Hartree–Fock limiting structure. Counterpoise estimates of the effects of basis set deficiencies on the structure and binding energy of this complex are shown to be misleading. Examination of the complexes (HF)2, (H2O)2, (NH3)2, (H2O)2H+, (HF)2H+, and F2H− at the MP4/6-311++G(3df ,3pd)//MP2/6-311++G(2d,2p) level of theory indicates that previous studies using fourth order perturbation theory with some smaller basis sets and Hartree–Fock optimized structures are likely to be reliable, although part of the agreement reflects a cancellation of error. HF/6-31+G(d) estimates of zero-point vibrational energy contributions to association energies are found to be satisfactory for asymmetric complexes, but can both over and underestimate the contribution of this term for symmetrically bound complexes.

Equations are presented for the analytic determination of dipole moment derivatives with respect to nuclear coordinates for closed-shell, open-shell unrestricted, and open-shell restricted Hartree–Fock wave functions. The efficient evaluation of these derivatives and the resulting infrared intensities simultaneously with determination of the vibrational frequencies is discussed. Intensities are presented for a selection of test molecules with a wide variety of basis sets. It is concluded that basis sets of double-zeta polarized or higher quality usually give correct qualitative information about the ordering of the intensities, while smaller basis sets may not even predict the most intense mode correctly. Quantitative accuracy using the larger basis sets seems to be limited primarily by the use of the double harmonic approximation.

Ab initio molecular orbital theory is used to examine the singlet and triplet potential energy surfaces for the CH2N+ system. The results confirm those of earlier studies which suggested that the singlet H2NC+ isomer could be formed via the corresponding triplet isomer. Also, it is shown that the reaction HCN+ + H2 might lead to this metastable isomer without invoking the triplet species. The best test of the hypothesis that this molecule can be formed by gas phase, ion molecule reactions and may be an important precursor in the interstellar synthesis of HCN and HNC is to search for it in space. To this end, theoretical predictions are made of its rotational frequencies and its vibrational frequencies and intensities to serve as a guide to laboratory spectroscopists and radioastronomers.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical study of the heats of formation of Si2Hn (n = 0-6) compounds and trisilanePauline Ho, Michael E. Coltrin, J. S. Binkley, and C. F. MeliusCite this: J. Phys. Chem. 1986, 90, 15, 3399–3406Publication Date (Print):July 1, 1986Publication History Published online1 May 2002Published inissue 1 July 1986https://pubs.acs.org/doi/10.1021/j100406a019https://doi.org/10.1021/j100406a019research-articleACS PublicationsRequest reuse permissionsArticle Views247Altmetric-Citations129LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts