@article{lamb_sremaniak_whitten_2013, title={Reaction pathways for butanoic acid decarboxylation on the (111) surface of a Pd nanoparticle}, volume={607}, ISSN={0039-6028}, url={http://dx.doi.org/10.1016/j.susc.2012.08.023}, DOI={10.1016/j.susc.2012.08.023}, abstractNote={Many-electron theory is applied to investigate decarboxylation of butanoic acid on the (111) surface of a Pd42 nanoparticle. Butanoic acid adsorbs weakly as an intact molecule (ΔH = − 28 kJ/mol) with the COOH moiety nearly parallel to the surface. In comparison, dissociative adsorption of butanoic acid to form surface butanoate (PrCOO) species and adsorbed H is exothermic by only 5 kJ/mol. Pathways for propane and CO2 formation are presented starting from adsorbed butanoic acid, PrCOO (ads) and a RCHCOO (R = C2H5) surface intermediate. An intramolecular pathway involves rotating the H of COOH toward the target (alpha) carbon. Following a series of bond distortions, the H is close enough to the target C to form a stretched HC bond. After propane begins to form, CO2 linearizes and CC dissociation is energetically favorable and rapid. Reaction of PrCOO (ads) and H (ads) also results in direct formation of propane and CO2. The energy barriers for H insertion are ~ 100 kJ/mol for both pathways; however, the dissociative pathway involves a high-energy precursor state with H in a 3-fold site under the CC bond undergoing reaction. An alternative decarboxylation pathway starting from RCHCOO leads to gas-phase CO2 and propylidene (in the absence of adsorbed H) or propyl (via insertion of adsorbed H) with energy barriers of 75 and 32 kJ/mol, respectively. The energy of the RCHCOO intermediate relative to gas-phase butanoic acid increases from 43 to 109 kJ/mol in the presence of adsorbed H, compensating for the lower decomposition barrier.}, journal={Surface Science}, publisher={Elsevier BV}, author={Lamb, H. Henry and Sremaniak, Laura and Whitten, Jerry L.}, year={2013}, month={Jan}, pages={130–137} }
 @article{sremaniak_whitten_menon_lucovsky_2003, title={Contributions to the infrared effective charges of oxides and chalcogenides from equilibrium charge and dynamic charge redistribution during normal mode motions}, volume={212}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(03)00087-4}, abstractNote={Empirical force constant models for infrared (IR) and Raman scattering have emphasized differences between non-crystalline oxides and chalcogenides, attributing them to different bond angles at the two-fold coordinated O- and S(Se)-atoms in spite of the fact that both classes of materials form continuous random networks (CRNs) with equivalent 8N rule bonding coordination. This article applies ab initio electronic structure calculations to determine (i) equilibrium bonding geometries, and (ii) infrared effective charges for normal mode motions of O- and S-atoms in SiO2, and GeS2 and As2S3, respectively. Differences in equilibrium bond angles and normal mode effective charges are shown to result from quantitative differences in SiO, and GeS and GeSe bond ionicities that optimize the SiO2, and GeS2 and As2S3 total energies at markedly different bond angles.}, number={2003 May 15}, journal={APPLIED SURFACE SCIENCE}, author={Sremaniak, LS and Whitten, JL and Menon, M and Lucovsky, G}, year={2003}, month={May}, pages={839–843} }
 @article{sremaniak_whitten_2002, title={Photoinduced dissociation of methylnitrite on Ag(111)}, volume={516}, ISSN={["1879-2758"]}, DOI={10.1016/S0039-6028(02)02037-X}, abstractNote={Electronic excitations and photoinduced electron attachment states of methylnitrite (CH3ONO) adsorbed on Ag(1 1 1) are investigated by ab initio methods. The calculated ground state energies of the cis and trans isomers of the methylnitrite molecule are nearly degenerate, with the trans structure lower than the cis by 0.03 eV at the CI level. Experimentally, the cis isomer is estimated to be more stable by 0.03 eV. The energy of methylnitrite in its ground electronic state on the silver surface is nearly the same for both isomer configurations and changes only slightly with isomer orientation and adsorption site. In both cis and trans forms, structures in which the internal oxygen points towards the surface and the O(internal)N internuclear axis lies between 30° and 45° from the surface are favored. The calculated adsorption energy is 0.60 eV for the cis isomer. Ground and excited state potential energy curves for dissociation to CH3O/Ag and NO (gas phase) are calculated at the CI level for both internal electronic excitations and for electron attachment excited states. The calculated ground state dissociation energy is 1.5 eV, a value 0.20 eV less than calculated for the gas phase dissociation. The metal-mediated excitation (electron attachment to the adsorbate and hole in the metal) leads to a repulsive triplet state with a vertical excitation energy of 4.7 eV and negligible singlet–triplet splitting. A second excited state produced by electron excitation within methylnitrite produces distinct singlet and triplet states. The vertical excitation occurs at 2.4 eV for the triplet state and at 3.4 eV for the singlet state. In comparing the methylnitrite/Ag(1 1 1) potential energy surface to that of gas phase methylnitrite, a shallow minimum in the first excited singlet state for the molecule appears only as a plateau in the adsorbate/metal system when the excitation is from within methylnitrite. There is a 10-fold increase in methylnitrite/silver mixing in the metal-mediated excitation as compared to the internal excitation, which may explain the surprising experimental result that dissociation does not follow metal-mediated excitation.}, number={3}, journal={SURFACE SCIENCE}, author={Sremaniak, LS and Whitten, JL}, year={2002}, month={Sep}, pages={254–264} }