The shear rate dependence of the slip length in thin polymer films confined between atomically flat surfaces is investigated by molecular dynamics simulations. The polymer melt is described by the bead-spring model of linear flexible chains. We found that at low shear rates the velocity profiles acquire a pronounced curvature near the wall and the absolute value of the negative slip length is approximately equal to the thickness of the viscous interfacial layer. At higher shear rates, the velocity profiles become linear and the slip length increases rapidly as a function of shear rate. The gradual transition from no-slip to steady-state slip flow is associated with faster relaxation of the polymer chains near the wall evaluated from decay of the time autocorrelation function of the first normal mode. We also show that at high melt densities the friction coefficient at the interface between the polymer melt and the solid wall follows a power-law decay as a function of the slip velocity. At large slip velocities the friction coefficient is determined by the product of the surface-induced peak in the structure factor, the temperature, and the contact density of the first fluid layer near the solid wall.

1 aPriezjev, N., V uhttps://icer.msu.edu/research/publications/shear-rate-threshold-boundary-slip-dense-polymer-films00397nas a2200133 4500008004100000245003800041210003800079300001200117490000700129100001900136700001900155700001200174856007700186 2009 eng d00aStrategies for Online Communities0 aStrategies for Online Communities a808-8220 v511 aMiller, K., D.1 aFabian, F., H.1 aLin, S. uhttps://icer.msu.edu/research/publications/strategies-online-communities01591nas a2200217 4500008004100000245007600041210006900117260001200186300001100198490000800209520092200217100001801139700001501157700001501172700001601187700001401203700001201217700001801229700001501247856011101262 2009 eng d00aSurvey of Excited State Neutron Spectroscopic Factors for Z=8-28 Nuclei0 aSurvey of Excited State Neutron Spectroscopic Factors for Z828 N c01/2009 a0625010 v1023 aWe have extracted 565 neutron spectroscopic factors of sd and fp shell nuclei by systematically analyzing more than 2000 measured (d, p) angular distributions. We are able to compare 125 of the extracted spectroscopic factors to values predicted by large-basis shell-model calculations and evaluate the accuracies of spectroscopic factors predicted by different shell-model interactions in these regions. We find that the spectroscopic factors predicted for most excited states of sd-shell nuclei using the latest {USDA} or {USDB} interactions agree with the experimental values. For fp shell nuclei, the inability of the current models to account for the core excitation and fragmentation of the states leads to considerable discrepancies. In particular, the agreement between data and shell-model predictions for Ni isotopes is not better than a factor of 2 using either the {GXPF1A} or the {XT} interaction.

1 aTsang, M., B.1 aLee, Jenny1 aSu, S., C.1 aDai, J., Y.1 aHoroi, M.1 aLiu, H.1 aLynch, W., G.1 aWarren, S. uhttps://icer.msu.edu/research/publications/survey-excited-state-neutron-spectroscopic-factors-z8-28-nuclei01604nas a2200193 4500008004100000245009100041210006900132260001200201490000700213520093400220653002301154653001501177653001601192653001801208653002801226100001801254700002001272856011801292 2008 eng d00aSlip boundary conditions for shear flow of polymer melts past atomically flat surfaces0 aSlip boundary conditions for shear flow of polymer melts past at c04/20080 v773 aMolecular dynamics simulations are carried out to investigate the dynamic behavior of the slip length in thin polymer films confined between atomically smooth thermal surfaces. For weak wall-fluid interactions, the shear rate dependence of the slip length acquires a distinct local minimum followed by a rapid growth at higher shear rates. With increasing fluid density, the position of the local minimum is shifted to lower shear rates. We found that the ratio of the shear viscosity to the slip length, which defines the friction coefficient at the liquid/solid interface, undergoes a transition from a nearly constant value to power law decay as a function of the slip velocity. In a wide range of shear rates and fluid densities, the friction coefficient is determined by the product of the value of the surface-induced peak in the structure factor and the contact density of the first fluid layer near the solid wall.

10amolecular dynamics10ashear rate10aslip length10aslip velocity10asmooth thermal surfaces1 aNiavarani, A.1 aPriezjev, N., V uhttps://icer.msu.edu/research/publications/slip-boundary-conditions-shear-flow-polymer-melts-past-atomically-flat02436nas a2200205 4500008004100000245012200041210006900163260001200232300001400244490000800258520172300266100001701989700001602006700001402022700001402036700001902050700001802069700001802087856012502105 2008 eng d00aStereoelectronic Effects on Molecular Geometries and State-Energy Splittings of Ligated Monocopper Diozygen Complexes0 aStereoelectronic Effects on Molecular Geometries and StateEnergy c03/2008 a3754-37670 v1123 aThe relative energies of side-on versus end-on binding of molecular oxygen to a supported Cu(I) species, and the singlet versus triplet nature of the ground electronic state, are sensitive to the nature of the supporting ligands and, in particular, depend upon their geometric arrangement relative to the O2 binding site. Highly correlated ab initio and density functional theory electronic structure calculations demonstrate that optimal overlap (and oxidative charge transfer) occurs for the side-on geometry, and this is promoted by ligands that raise the energy, thereby enhancing resonance, of the filled Cu dxz orbital that hybridizes with the in-plane π* orbital of O2. Conversely, ligands that raise the energy of the filled Cu dz2 orbital foster a preference for end-on binding as this is the only mode that permits good overlap with the in-plane O2 π*. Because the overlap of Cu dz2 with O2 π* is reduced as compared to the overlap of Cu dxz with the same O2 orbital, the resonance is also reduced, leading to generally more stable triplet states relative to singlets in the end-on geometry as compared to the side-on geometry, where singlet ground states become more easily accessible once ligands are stronger donors. Biradical Cu(II)-O2 superoxide character in the electronic structure of the supported complexes leads to significant challenges for accurate quantum chemical calculations that are best addressed by exploiting the spin-purified M06L local density functional, single-reference completely renormalized coupled-cluster theory, or multireference second-order perturbation theory, all of which provide predictions that are qualitatively and quantitatively consistent with one another.

1 aCramer, C.J.1 aGour, J., R1 aKinal, A.1 aWloch, M.1 aPiecuch, Piotr1 aShahi, A.R.M.1 aGagliardi, L. uhttps://icer.msu.edu/research/publications/stereoelectronic-effects-molecular-geometries-state-energy-splittings-ligated02163nas a2200193 4500008004100000245008900041210006900130260001200199300001200211490000800223520143600231653002801667653008201695100001701777700001701794700001901811700001701830856012201847 2008 eng d00aThe Structure of Partially-Premixed Methane Flames in High Intensity Turbulent Flows0 aStructure of PartiallyPremixed Methane Flames in High Intensity c09/2008 a692-7140 v1543 aDirect numerical simulations (DNS) are conducted to study the structure of partially premixed and non-premixed methane flames in high-intensity two-dimensional isotropic turbulent flows. The results obtained via “flame normal analysis” show local extinction and reignition for both non-premixed and partially premixed flames. Dynamical analysis of the flame with a Lagrangian method indicates that the time integrated strain rate characterizes the finite-rate chemistry effects and the flame extinction better than the strain rate. It is observed that the flame behavior is affected by the “pressure-dilatation” and “viscous-dissipation” in addition to strain rate. Consistent with previous studies, high vorticity values are detected close to the reaction zone, where the vorticity generation by the “baroclinic torque” was found to be significant. The influences of (initial) Reynolds and Damköhler numbers, and various air–fuel premixing levels on flame and turbulence variables are also studied. It is observed that the flame extinction occurs similarly in flames with different fuel–air premixing. Our simulations also indicate that the CO emission increases as the partial premixing of the fuel with air increases. Higher values of the temperature, the OH mass fraction and the CO mass fraction are observed within the flame zone at higher Reynolds numbers.

10aDNS; Methane combustion10aturbulent reacting flows; partially premixed flames; reduced chemistry models1 aYaldizli, M.1 aMohammad, H.1 aMehravaran, K.1 aJaberi, F.A. uhttps://icer.msu.edu/research/publications/structure-partially-premixed-methane-flames-high-intensity-turbulent-flows01279nas a2200457 4500008004100000245014900041210006900190260001200259490000700271100001700278700001500295700001600310700001500326700001700341700001600358700001400374700001400388700001800402700001600420700001300436700001600449700001900465700001500484700001700499700001400516700001400530700001400544700001500558700001600573700001700589700001700606700001700623700001500640700001700655700001400672700001400686700001300700700001800713700001900731856007100750 2007 eng d00aShape and Structure of N = Z 64Ge: Electromagnetic Transition Rates from the Application ￼of the Recoil Distance Method to a Knockout Reaction0 aShape and Structure of N Z 64Ge Electromagnetic Transition Rates c07/20070 v991 aStarosta, K.1 aDewald, A.1 aDunomes, A.1 aAdrich, P.1 aAmthor, A.M.1 aBaumann, T.1 aBazin, D.1 aBowen, M.1 aBrown, B., A.1 aChester, A.1 aGade, A.1 aGalaviz, D.1 aGlasmacher, T.1 aGinter, T.1 aHausmann, M.1 aHoroi, M.1 aJolie, J.1 aMelon, B.1 aMiller, D.1 aMoeller, V.1 aNorris, R.P.1 aPissulla, T.1 aPortillo, M.1 aRother, W.1 aShimbara, Y.1 aStolz, A.1 aVaman, C.1 aVoss, P.1 aWeisshaar, D.1 aZelevinsky, V. uhttp://journals.aps.org/prl/abstract/10.1103/PhysRevLett.99.04250300506nas a2200157 4500008004100000245007300041210006900114260001200183490000700195100001400202700001800216700001500234700001400249700001700263856006800280 2006 eng d00aShell model analysis of the 56Ni spectrum in the full pf model space0 aShell model analysis of the 56Ni spectrum in the full pf model s c06/20060 v731 aHoroi, M.1 aBrown, B., A.1 aOtsuka, T.1 aHonma, M.1 aMizusaki, T. uhttp://journals.aps.org/prc/abstract/10.1103/PhysRevC.73.06130501338nas a2200169 4500008004100000245011100041210006900152260001200221300001400233490000800247520073400255100001900989700001401008700001601022700001401038856011601052 2006 eng d00aSingle-reference, size-extensive, non-iterative coupled-cluster approaches to bond breaking and biradicals0 aSinglereference sizeextensive noniterative coupledcluster approa c02/2006 a467–4740 v4183 aWe propose the non-iterative, completely renormalized (CR) coupled-cluster (CC) approaches, including the CR-CC(2, 3) method which offers considerable improvements over the CCSD(T) approach without a significant increase in the computer effort. The CR-CC(2, 3) method, in which the CCSD (CC singles and doubles) energy is corrected for the effect of triples, is size extensive, competitive with CCSD(T) in calculations for non-degenerate states, and as accurate as the expensive CC approach with singles, doubles, and triples in the bond-breaking region. Calculations of the activation enthalpy for the thermal isomerizations of cyclopropane involving trimethylene suggest that CR-CC(2, 3) may be applicable to biradicals.

1 aPiecuch, Piotr1 aWloch, M.1 aGour, J., R1 aKinal, A. uhttps://icer.msu.edu/single-reference-size-extensive-non-iterative-coupled-cluster-approaches-bond-breaking-and