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1. Uncommonly accurate energies for the general quartic oscillator

   https://doi.org/https://doi.org/10.1002/qua.26554  

   Okun, Pavel; Burke, Kieron (November 2020, International journal of quantum chemistry)

   Recent advances in the asymptotic analysis of energy levels of potentials produce relative errors ineigenvalue sums of order10−34, but few non-trivial potentials have been solved numerically to such accuracy. We solve the general quartic potential (arbitrary linear combination ofx2andx4) beyond this level of accuracy using a basis of several hundred oscillator states. We list the lowest 20 eigenvalues for 9 such potentials. We confirm the known asymptotic expansion for the levels of the pure quarticoscillator, and extract the next 2 terms in the asymptotic expansion. We give analytic formulas for expansion in up to 3 even basis states. We confirm the virial theorem for the various energy components to similar accuracy. The sextic oscillator levels are also given. These benchmark results should be useful for extreme tests of approximations in several areas of chemical physics and beyond. 

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2. Activation Energies and Beyond

   https://doi.org/10.1021/acs.jpca.9b03967  

   Piskulich, Zeke A.; Mesele, Oluwaseun O.; Thompson, Ward H. (August 2019, The Journal of Physical Chemistry A)
3. The Viscous Surface Wave Problem with Generalized Surface Energies

   https://doi.org/10.1137/18M1195851  

   Remond-Tiedrez, Antoine; Tice, Ian (January 2019, SIAM Journal on Mathematical Analysis)
4. Extrapolation of high-order correlation energies: the WMS model

   https://doi.org/10.1039/C8CP04973D  

   Zhao, Yan; Xia, Lixue; Liao, Xiaobin; He, Qiu; Zhao, Maria X.; Truhlar, Donald G. (November 2018, Physical Chemistry Chemical Physics)

   We have developed a new composite model chemistry method called WMS (Wuhan–Minnesota scaling method) with three characteristics: (1) a composite scheme to approximate the complete configuration interaction valence energy with the affordability condition of requiring no calculation more expensive than CCSD(T)/jul-cc-pV(T+d)Z, (2) low-cost methods for the inner-shell correlation contribution and scalar relativistic correction, and (3) accuracy comparable to methods with post-CCSD(T) components. The new method is shown to be accurate for the W4-17 database of 200 atomization energies with an average mean unsigned error (averaged with equal weight over strongly correlated and weakly correlated subsets of the data) of 0.45 kcal mol −1 , and the performance/cost ratio of these results compares very favorably to previously available methods. We also assess the WMS method against the DBH24-W4 database of diverse barrier heights and the energetics of the reactions of three strongly correlated Criegee intermediates with water. These results demonstrate that higher-order correlation contributions necessary to obtain high accuracy for molecular thermochemistry may be successfully extrapolated from the lower-order components of CCSD(T) calculations, and chemical accuracy can now be obtained for larger and more complex molecules and reactions. 

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5. Ionization energies and cationic bond dissociation energies of RuB, RhB, OsB, IrB, and PtB

   https://doi.org/10.1063/5.0107086  

   Merriles, Dakota M.; Morse, Michael D. (August 2022, The Journal of Chemical Physics)

   Two-photon ionization thresholds of RuB, RhB, OsB, IrB, and PtB have been measured using resonant two-photon ionization spectroscopy in a jet-cooled molecular beam and have been used to derive the adiabatic ionization energies of these molecules. From the measured two-photon ionization thresholds, IE(RuB) = 7.879(9) eV, IE(RhB) = 8.234(10) eV, IE(OsB) = 7.955(9) eV, IE(IrB) = 8.301(15) eV, and IE(PtB) = 8.524(10) eV have been assigned. By employing a thermochemical cycle, cationic bond dissociation energies of these molecules have also been derived, giving D0(Ru+–B) = 4.297(9) eV, D0(Rh+–B) = 4.477(10) eV, D0(Os–B+) = 4.721(9) eV, D0(Ir–B+) = 4.925(18) eV, and D0(Pt–B+) = 5.009(10) eV. The electronic structures of the resulting cationic transition metal monoborides (MB+) have been elucidated using quantum chemical calculations. Periodic trends of the MB+ molecules and comparisons to their neutral counterparts are discussed. The possibility of quadruple chemical bonds in all of these cationic transition metal monoborides is also discussed. 

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