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Publication Metadata only Bosonic helium clusters doped by alkali metal cations: interaction forces and analysis of their most stable structures(Springer, 2007) Marinetti, Fabio; Coccia, Emanuele; Bodo, Enrico; Gianturco, Franco A.; Yurtsever, Mine; Yıldırım, Erol; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Ab initio potentials are computed for alkali metal cationic partners interacting with He-4 and an overall many-body potential is constructed for each of the ionic dopants in helium clusters. The structures are then obtained via a genetic algorithm approach and results compared with Basin-Hopping Monte Carlo simulations. The classical arrangements are analyzed and quantum effects discussed in comparison with what has been found with Diffusion Monte Carlo calculations. Further corrections to the classical picture by including three-body forces and radial delocalization of the helium adatoms are also considered and their effects analyzed.Publication Metadata only Competitive hydrogen bonding in aspirin-aspirin and aspirin-leucine interactions(Scientific Technical Research Council Turkey-Tubitak, 2012) Department of Chemistry; Department of Chemical and Biological Engineering; Department of Chemistry; Yurtsever, Zeynep; Erman, Burak; Yurtsever, İsmail Ersin; Undergraduate Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; College of Sciences; College of Engineering; College of Sciences; N/A; 179997; 7129Aspirin-aspirin and aspirin-leucine interactions are studied by the density functional theory (DFT) and high level ab initio calculations with second order Moller-Plesset perturbation theory (MP2). The rotational isomers of aspirin are identified by their relative stability both in gaseous phase and in water using the polarizable continuum method (PCM). Local minima of aspirin monomers in water are found to be all highly populated compared to the gas phase behavior. Homodimers of aspirin form hydrogen bonds with bond energies of 10 kcal/mol. Weak hydrogen bonds utilizing phenyl and methyl groups are also found. The interaction between aspirin and leucine is stronger with relatively short bond lengths compared to homodimeric aspirin interactions. The potential energy surface has several minima with comparable stability. This study shows the significance of diverse bonding schemes, which are important for understanding complete interaction mechanisms of aspirin.Publication Metadata only Inferring transferable intermolecular potential models(2008) Üçyigitler, Sinan; Çamurdan, Mehmet C.; Elliott, J. Richard; Department of Industrial Engineering; Türkay, Metin; Faculty Member; Department of Industrial Engineering; College of Engineering; 24956Discontinuous molecular dynamics is combined with thermodynamic perturbation theory to provide an efficient basis for characterising molecular interactions based on vapour pressure and liquid density data. Several prospective potential models are discretised to permit treatment by Barker–Henderson perturbation theory. The potentials are characterised by 11 wells ranging over radial distances from the site diameter to three times that diameter. Considered potential models include the Lennard-Jones (LJ), square-well, Yukawa (Yuk) and multi-line potentials, and their combinations. The optimal model is found to be a combination of square-well and Yuk potentials, with the switch position and Yuk decay set to universal values. This model provides average vapour pressure deviations of less than 10% for a database of 86 aliphatic, aromatic and naphthenic compounds. The LJ potential provides the least competitive accuracy. Considering statistical information criteria facilitates the identification of the optimal model.Publication Metadata only Nanoparticle silicalite-1 crystallization from clear solutions: nucleation(Elsevier Science Bv, 2009) Tokay, Begüm; Erdem-Şenatalar, Ayşe; Schueth, Ferdi; Thompson, Robert W.; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882Despite much effort spent by various research groups, there remain many aspects of nanoparticle silicalite-1 crystallization from clear solutions which require further investigation. In order to shed light, especially on the nucleation of silicalite-1, particle growth at 100 degrees C from several starting compositions known to yield colloidal silicalite-1, which have been studied previously by other researchers using various techniques, was followed in this study by laser light scattering using scattering angles of 90 degrees and 173 degrees, and zeta potential and pH measurements. Crystallinity was monitored by X-ray diffraction, Fourier transform infrared analysis and transmission electron microscopy. Thermogravimetric analyses and density measurements were also used to characterize the products obtained at various times during the syntheses. The results demonstrate that the distinct time of sudden jump in the effective diameter of the nanoparticles in solution, as observed more clearly by using the back-scattering device, and which marks the beginning of the constant linear growth rate of the particles, corresponds to the nucleation of the silicalite-1 crystal structure. This time was also shown to coincide with the exo-endo thermal switch time of the reaction mechanism, which has been observed previously by another research group. Nucleation was accompanied by an aggregation of a population of smaller particles, as indicated by the broadening of the particle size distribution, and the variation of the pH and zeta potential values during synthesis.Publication Metadata only Rotational cooling of Li-2((1)sigma(+)(g)) molecules by ultracold collisions with a helium gas buffer(Springer, 2004) Bodo, E; Gianturco, F. A.; Sebastianelli, F; Yurtsever, M.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129The very weak interaction of Li-2 with He atoms has been obtained from accurate ab initio calculations and is here analyzed in terms of its anisotropic features. Quantum scattering calculations of the rotational inelastic de-excitation cross sections are carried out using a recently proposed multichannel treatment, the modified variable phase method, implemented by the authors and applied here to ultralow collision energies. General conclusions on the low efficiency of a He buffer gas in cooling down molecular rotations in this system are presented and analyzed.Publication Metadata only Rotational cooling of Li-2((1)sigma(+)(g))molecules by ultracold collisions with an he gas buffer (vol 112, pg 263, 2004)(Springer, 2005) Bodo, E; Gianturco, F. A.; Sebastianelli, F; Yurtsever, M.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129N/APublication Metadata only Stacking of triphenylene: characterization of the potential energy surface(Springer, 2010) Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129The interaction potential energy of triphenylene dimer has been calculated with Møller–Plesset second-order perturbation theory for various geometrical configurations. Different types of geometrical perturbations such as rotation, displacements and their combinations are studied in terms of their effects on the stability of the dimer. Minimum energy conformers for face to face, rotated, parallel displaced and T-shape structures are obtained. For the unsubstituted triphenylene, the 35° rotation of one of the monomers results in the global minimum. However, the dimer is still very flexible in terms of displacements. A helical structure seems to be the most stable form for the trimer. For large stacked clusters, the two body forces dominate the interactions while at small monomer–monomer separation, three body terms behave like z −9 where z is the vertical distance between two adjacent monomers.Publication Metadata only The metastable structures of anthracene-argon clusters inside helium nanodroplets(Springer, 2021) Calvo, Florent; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Recent experiments have revealed that anthracene forms rather diverse complexes with multiple argon atoms upon embedding in helium nanodroplets. In this work we have modeled such complexes and investigated the relative stability of various isomeric forms using classical force fields reparametrized on electronic structure data at the level of spin-component scaled MP2, nuclear quantum effects being accounted for by means of path-integral molecular dynamics simulations. We generally find that the structures obtained are very sensitive to the details of the potential, but also to the inclusion of zero- point motion, for which the harmonic approximation is found to be generally accurate. Inside He-1000 clusters, the complexes also exhibit different relative stabilities, the quantum solvent usually favoring more asymmetric complexes. No evidence for fluxionality at 1 K in a given cluster is found. Using ring-polymer molecular dynamics trajectories, the stability of an argon dimer initially distant from the anthracene molecule was also investigated. Such metastable configurations are found to have a lifetime of the order of nanoseconds, confirming the possibility of trapping them in experiments.