@article{ChoudhuryDeVineSinhaetal.2022,
  author    = {Choudhury, Arnab and DeVine, Jessalyn A. A. and Sinha, Shreya and Lau, Jascha Alexander and Kandratsenka, Alexander and Schwarzer, Dirk and Saalfrank, Peter and Wodtke, Alec Michael},
  title     = {Condensed-phase isomerization through tunnelling gateways},
  series = {Nature : the international weekly journal of science},
  volume    = {612},
  journal   = {Nature : the international weekly journal of science},
  number    = {7941},
  publisher = {Macmillan Publishers Limited, part of Springer Nature},
  address   = {London},
  issn      = {0028-0836},
  doi       = {10.1038/s41586-022-05451-0},
  pages     = {691 -- 695},
  year      = {2022},
  abstract  = {Quantum mechanical tunnelling describes transmission of matter waves through a barrier with height larger than the energy of the wave(1). Tunnelling becomes important when the de Broglie wavelength of the particle exceeds the barrier thickness; because wavelength increases with decreasing mass, lighter particles tunnel more efficiently than heavier ones. However, there exist examples in condensed-phase chemistry where increasing mass leads to increased tunnelling rates(2). In contrast to the textbook approach, which considers transitions between continuum states, condensed-phase reactions involve transitions between bound states of reactants and products. Here this conceptual distinction is highlighted by experimental measurements of isotopologue-specific tunnelling rates for CO rotational isomerization at an NaCl surface(3,4), showing nonmonotonic mass dependence. A quantum rate theory of isomerization is developed wherein transitions between sub-barrier reactant and product states occur through interaction with the environment. Tunnelling is fastest for specific pairs of states (gateways), the quantum mechanical details of which lead to enhanced cross-barrier coupling; the energies of these gateways arise nonsystematically, giving an erratic mass dependence. Gateways also accelerate ground-state isomerization, acting as leaky holes through the reaction barrier. This simple model provides a way to account for tunnelling in condensed-phase chemistry, and indicates that heavy-atom tunnelling may be more important than typically assumed.},
  language  = {en}
}
@article{LindicSinhaMattssonetal.2022,
  author    = {Lindic, Tilen and Sinha, Shreya and Mattsson, Stefan and Paulus, Beate},
  title     = {Prediction of a model crystal structure for Ni2F5 by first-principles calculations},
  series = {Zeitschrift f{\"u}r Naturforschung : B, Chemical sciences},
  volume    = {77},
  journal   = {Zeitschrift f{\"u}r Naturforschung : B, Chemical sciences},
  number    = {6},
  publisher = {De Gruyter},
  address   = {Berlin},
  issn      = {0932-0776},
  doi       = {10.1515/znb-2022-0072},
  pages     = {469 -- 473},
  year      = {2022},
  abstract  = {Electrochemical fluorination in anhydrous HF, also known as the Simons process, is a widely used industrial method for fluorination of organic compounds. Its mechanism, being not so well understood, has long been debated and is believed to involve higher valent nickel fluorides formed on the nickel-plated anode during the process. One of these is speculated to be Ni2F5, which was previously reported in the literature and assigned via infrared spectroscopy, but its crystal structure is not yet known. We have identified known crystal structures of compounds with similar stoichiometries as Ni2F5 and utilized them as a starting point for our periodic DFT investigations, applying the PBE+U method. Ni2F5 as the most stable polymorph was found to be of the same crystal structure as another mixed valent fluoride, Cr2F5. The calculated lattice parameters are a = 7.24 angstrom, b = 7.40 angstrom, c = 7.08 angstrom and beta = 118.9 degrees with an antiferromagnetic ordering of the nickel magnetic moments.},
  language  = {en}
}
@article{SinhaSaalfrank2021,
  author    = {Sinha, Shreya and Saalfrank, Peter},
  title     = {"Inverted" CO molecules on NaCl(100)},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {23},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {13},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/d0cp05198e},
  pages     = {7860 -- 7874},
  year      = {2021},
  abstract  = {Somewhat surprisingly, inverted ("O-down") CO adsorbates on NaCl(100) were recently observed experimentally after infrared vibrational excitation (Lau et al., Science, 2020, 367, 175-178). Here we characterize these species using periodic density functional theory and a quantum mechanical description of vibrations. We determine stationary points and minimum energy paths for CO inversion, for low (1/8 and 1/4 monolayers (ML)) and high (1 ML) coverages. Transition state theory is applied to estimate thermal rates for "C-down" to "O-down" isomerization and the reverse process. For the 1/4 ML p(1 x 1) structure, two-dimensional and three-dimensional potential energy surfaces and corresponding anharmonic vibrational eigenstates obtained from the time-independent nuclear Schrodinger equation are presented. We find (i) rather coverage-independent CO inversion energies (of about 0.08 eV or 8 kJ mol(-1) per CO) and corresponding classical activation energies for "C-down" to "O-down" isomerization (of about 0.15 eV or 14 kJ mol(-1) per CO); (ii) thermal isomerization rates at 22 K which are vanishingly small for the "C-down" to "O-down" isomerization but non-negligible for the back reaction; (iii) several "accidentally degenerate" pairs of eigenstates well below the barrier, each pair describing "C-down" to "O-down" localized states.},
  language  = {en}
}