Adsorption and Diffusion of Oxygen on Pure and Partially Oxidized Metal Surfaces in Ultrahigh Resolution

Abstract

The interaction of gas molecules with metal and oxide surfaces plays a critical role in corrosion, catalysis, sensing, and heterogeneous materials. However, insights into the dynamics of O2 from picoseconds to microseconds have remained unavailable to date. We obtained 3D potential energy surfaces for adsorption of O2 on 11 common pristine and partially oxidized (hkl) surfaces of Ni and Al in picometer resolution and high accuracy of 0.1 kcal/mol, identified binding sites, and surface mobility from 25 to 300 °C. We explain relative oxidation rates and parameters for oxide growth. We employed over 150 000 molecular mechanics and molecular dynamics simulations with the interface force field (IFF) using structural data from X-ray diffraction (XRD) and low-energy electron diffraction (LEED). The methods reach 10 to 50 times higher accuracy than possible before and are suited to analyze gas interactions with metals up to the micrometer scale including defects and irregular nanostructures.

Accurate and Ultrafast Simulation of Molecular Recognition and Assembly on Metal Surfaces in Four Dimensions

“…Developments for a wide range of metal oxide surfaces are in progress. If not currently available, parameters can be estimated with moderate effort by chemical analogy for semiquantitative predictions, or derived and validated in full accuracy following the IFF protocol (see refs , ). In comparison, quantum methods including DFT can be applied to any chemistry; however, questions about reliability and scalability remain, and the computational speed is a million times lower (Figure S1 in the Supporting Information).…”

“…Due to surface reactions and oxidation of elemental metals, it can also be important to incorporate metal oxides, hydroxides, and other compounds. The simulation methods can be applied to such interfaces in principle, whereby the oxides and hydroxides require dedicated IFF parameters, as currently available for silica, alumina, nickel oxide, , calcium oxide and hydroxide, , and molybdenum oxide . Developments for a wide range of metal oxide surfaces are in progress.…”

“…IFF models can also be applied to metal/metal oxide surfaces and several oxide parameters are available, although not yet as extensively as for metals. 31,55,56 IFF uses a classical, quantum mechanically justified, widely used energy expression, available in Class I and Class II formats, and relatively few, interpretable parameters. 33 Other Class I force fields include CVFF, 68 CHARMM, 69 DREIDING, 70 GROMOS, 71 AMBER/ GAFF, 72 and OPLS-AA.…”

“…As a result, MD simulations become more reliable and more transparent than earlier models, as well as applicable to an unlimited range of metal–organic and metal–electrolyte interfaces. IFF models can also be applied to metal/metal oxide surfaces and several oxide parameters are available, although not yet as extensively as for metals. ,, …”

“…In addition, the approximations in quantum mechanical methods such as DFT that are necessary to facilitate calculations on many-electron metal surfaces and organic molecules involve major compromises. For example, ab initio molecular dynamics simulations of reactions on nanoscale surfaces complete new bond formation after a few picoseconds, which is known to take milliseconds in experiments . The mismatch by about 9 orders of magnitude poses a grand challenge toward understanding the true timeline of molecular events, and solutions have yet to be identified.…”