Using first principle electronic structure calculations within density functional theory and the supercell model, we have investigated the nature and formation energies of defect states associated with Ga and Te vacancies and Ge and Sn substitutional impurities in GaTe. We have also calculated the band structure of pure GaTe for comparison with systems with defects and also to find out the importance of spin–orbit interaction (SOI) on its band structure. We find that the top valence band at the Γ-point shifts up in energy by 0.1 eV due to the mixing of Te p x –p y and p z bands, this splitting being considerably smaller than in atoms where it is 0.8 eV. From an analysis of charge densities and band structures associated with the defect states, we find that most of them are strongly localized and lie deep in the band gap region. The calculated binding energy of the deep defect state and the ε(−1 / −2) transition level associated with the Ga vacancy appears to be in good agreement with experiment. Formation energy calculations suggest that V Ga is the preferred intrinsic defect in GaTe.

1 aRak, Zs1 aMahanti, S., D.1 aMandal, Krishna, C1 aFernelius, N.C. uhttps://icer.msu.edu/research/publications/theoretical-studies-defect-states-gate-002667nas a2200157 4500008004100000245008500041210006900126260001200195300001400207490000800221520211000229100001902339700001302358700001802371856012002389 2009 eng d00aThermochemical Kinetics for Multi-reference Systems: Addition Reactions of Ozone0 aThermochemical Kinetics for Multireference Systems Addition Reac c04/2009 a5786-57990 v1133 aThe 1,3-dipolar cycloadditions of ozone to ethyne and ethene provide extreme examples of multireference singlet-state chemistry, and they are examined here to test the applicability of several approaches to thermochemical kinetics of systems with large static correlation. Four different multireference diagnostics are applied to measure the multireference characters of the reactants, products, and transition states; all diagnostics indicate significant multireference character in the reactant portion of the potential energy surfaces. We make a more complete estimation of the effect of quadruple excitations than was previously available, and we use this with CCSDT/CBS estimation of Wheeler et al. (Wheeler, S. E.; Ess, D. H.; Houk, K. N. J. Phys. Chem. A 2008, 112, 1798.) to make new best estimates of the van der Waals association energy, the barrier height, and the reaction energy to form the cycloadduct for both reactions. Comparing with these best estimates, we present comprehensive mean unsigned errors for a variety of coupled cluster, multilevel, and density functional methods. Several computational aspects of multireference reactions are considered: (i) the applicability of multilevel theory, (ii) the convergence of coupled cluster theory for reaction barrier heights, (iii) the applicability of completely renormalized coupled cluster methods to multireference systems, (iv) the treatment by density functional theory, (v) the multireference perturbation theory for multireference reactions, and (vi) the relative accuracy of scaling-type multilevel methods as compared with additive ones. It is found that scaling-type multilevel methods do not perform better than the additive-type multilevel methods. Among the 48 tested density functionals, only M05 reproduces the best estimates within their uncertainty. Multireference perturbation theory based on the complete-active-space reference wave functions constructed using a small number of reaction-specific active orbitals gives accurate forward barrier heights; however, it significantly underestimates reaction energies.

1 aPiecuch, Piotr1 aZhao, Y.1 aTruhlar, D.G. uhttps://icer.msu.edu/research/publications/thermochemical-kinetics-multi-reference-systems-addition-reactions-ozone00639nas a2200193 4500008004100000245007100041210006900112260000800181300001200189490000800201653001900209653002100228100001800249700001700267700001900284700001900303700001900322856010400341 2009 eng d00aThree Modes of Metal-Enriched Star Formation in the Early Universe0 aThree Modes of MetalEnriched Star Formation in the Early Univers cjan a441-4510 v69110aearly universe10astars: formation1 aSmith, B., D.1 aTurk, M., J.1 aSigurdsson, S.1 aO'Shea, B., W.1 aNorman, M., L. uhttps://icer.msu.edu/research/publications/three-modes-metal-enriched-star-formation-early-universe01702nas a2200133 4500008004100000245007000041210006800111260001200179490000700191520123400198100001101432700001701443856010801460 2009 eng d00aTurbulence-Interface Interactions in a Two-Fluid Homogeneous Flow0 aTurbulenceInterface Interactions in a TwoFluid Homogeneous Flow c09/20090 v213 aThe two-way interactions between the turbulent velocity field and the interface in an incompressible two-fluid homogeneous turbulent flow are studied with a recently developed Lagrangian–Eulerian interfacial particle level-set method. The numerical results confirm that the rate of change of the interface area is directly related to the work done by the surface tension force. While the surface tension damps the surrounding turbulence in the “interface stretching period” to oppose the increase in interface area, it is shown to actually increase the turbulent kinetic energy when the interface experiences compression. Additionally, the surface tension force is found to generate strong vortical motions close to the interface through the baroclinic torque effects. There is also an increase in strain rate and the viscous dissipation rate of turbulent kinetic energy in the interface region. The effect of interface on the surrounding turbulence appears primarily in the direction perpendicular to the interface. Analysis of the vorticity and kinetic energy equations indicates that the turbulence-interface interactions are strongly dependent on the fluids’ density ratio and the Weber number.

1 aLi, Z.1 aJaberi, F.A. uhttps://icer.msu.edu/research/publications/turbulence-interface-interactions-two-fluid-homogeneous-flow00488nas a2200157 4500008004100000245004900041210004900090260001200139300001100151490000700162100001200169700002000181700002300201700002000224856008600244 2008 eng d00aTheoretical studies of defect states in GaTe0 aTheoretical studies of defect states in GaTe c01/2009 a0155040 v211 aRak, Zs1 aMahanti, S., D.1 aMandal, Krishna, C1 aFernelius, N.C. uhttps://icer.msu.edu/research/publications/theoretical-studies-defect-states-gate01816nas a2200217 4500008004100000245009100041210006900132260001200201490000700213520109300220653002301313653001901336100001401355700001801369700001601387700001201403700002001415700001801435700001901453856012601472 2008 eng d00aTransport Model Simulations of Projectile Fragmentation Reactions at 140 {MeV/nucleon}0 aTransport Model Simulations of Projectile Fragmentation Reaction c08/20080 v783 aThe collisions in four different reaction systems using {\$ˆ{40,48}\$Ca} and {\$ˆ{58,64}\$Ni} isotope beams and a Be target have been simulated using the Heavy Ion Phase Space Exploration and the Antisymmetrized Molecular Dynamics models. The present study mainly focuses on the model predictions for the excitation energies of the hot fragments and the cross sections of the final fragments produced in these reactions. The effects of various factors influencing the final fragment cross sections, such as the choice of the statistical decay code and its parameters have been explored. The predicted fragment cross sections are compared to the projectile fragmentation cross sections measured with the A1900 mass separator. At {\$E/A=140\$} {MeV,} reaction dynamics can significantly modify the detection efficiencies for the fragments and make them different from the efficiencies applied to the measured data reported in the previous work. The effects of efficiency corrections on the validation of event generator codes are discussed in the context of the two models.

10aNuclear Experiment10aNuclear Theory1 aMocko, M.1 aTsang, M., B.1 aLacroix, D.1 aOno, A.1 aDanielewicz, P.1 aLynch, W., G.1 aCharity, R., J uhttps://icer.msu.edu/research/publications/transport-model-simulations-projectile-fragmentation-reactions-140-mev-nucleon01465nas a2200181 4500008004100000245010100041210006900142260001500211300001600226490000800242520084100250100001701091700001401108700001401122700001901136700001801155856011001173 2006 eng d00aTheoretical Characterization of End-on and Side-on Peroxide Coordination in Ligated Cu2O2 Models0 aTheoretical Characterization of Endon and Sideon Peroxide Coordi c09/15/2006 a11557-115680 v1103 aThe relative energetics of μ-η1:η1 (trans end-on) and μ-η2:η2 (side-on) peroxo isomers of Cu2O2 fragments supported by 0, 2, 4, and 6 ammonia ligands have been computed with various density functional, coupled-cluster, and multiconfigurational protocols. There is substantial disagreement between the different levels for most cases, although completely renormalized coupled-cluster methods appear to offer the most reliable predictions. The significant biradical character of the end-on peroxo isomer proves problematic for the density functionals, while the demands on active space size and the need to account for interactions between different states in second-order perturbation theory prove challenging for the multireference treatments. In the latter case, it proved impossible to achieve any convincing convergence.

1 aCramer, C.J.1 aKinal, A.1 aWloch, M.1 aPiecuch, Piotr1 aGagliardi, L. uhttps://icer.msu.edu/theoretical-characterization-end-and-side-peroxide-coordination-ligated-cu2o2-models02131nas a2200181 4500008004100000245012100041210006900162260001200231300001600243490000800259520146800267100001701735700001401752700001901766700002401785700001801809856012201827 2006 eng d00aTheoretical Models on the Cu2O2 Torture Track. Mechanistic Implications for Oxytyrosinase and Small-molecule Analogs0 aTheoretical Models on the Cu2O2 Torture Track Mechanistic Implic c06/2007 a1991–20040 v1103 aAccurately describing the relative energetics of alternative bis(mu-oxo) and mu-eta2:eta2 peroxo isomers of Cu2O2 cores supported by 0, 2, 4, and 6 ammonia ligands is remarkably challenging for a wide variety of theoretical models, primarily owing to the difficulty of maintaining a balanced description of rapidly changing dynamical and nondynamical electron correlation effects and a varying degree of biradical character along the isomerization coordinate. The completely renormalized coupled-cluster level of theory including triple excitations and extremely efficient pure density functional levels of theory quantitatively agree with one another and also agree qualitatively with experimental results for Cu2O2 cores supported by analogous but larger ligands. Standard coupled-cluster methods, such as CCSD(T), are in most cases considerably less accurate and exhibit poor convergence in predicted relative energies. Hybrid density functionals significantly underestimate the stability of the bis(mu-oxo) form, with the magnitude of the error being directly proportional to the percentage Hartree-Fock exchange in the functional. Single-root CASPT2 multireference second-order perturbation theory, by contrast, significantly overestimates the stability of bis(mu-oxo) isomers. Implications of these results for modeling the mechanism of C-H bond activation by supported Cu2O2 cores, like that found in the active site of oxytyrosinase, are discussed.

1 aCramer, C.J.1 aWloch, M.1 aPiecuch, Piotr1 aPuzzarini, Cristina1 aGagliardi, L. uhttps://icer.msu.edu/theoretical-models-cu2o2-torture-track-mechanistic-implications-oxytyrosinase-and-small-molecule00614nas a2200157 4500008004100000245012500041210006900166260001100235300001400246490000800260100001900268700001400287700002100301700001600322856011800338 2006 eng d00aTwo New Classes of Non-Iterative Coupled-Cluster Methods Derived from the Method of Moments of Coupled-Cluster Equations0 aTwo New Classes of NonIterative CoupledCluster Methods Derived f c7/2006 a2149-21720 v1041 aPiecuch, Piotr1 aWloch, M.1 aLogriguito, M.D.1 aGour, J., R uhttps://icer.msu.edu/two-new-classes-non-iterative-coupled-cluster-methods-derived-method-moments-coupled-cluster