Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Cong Liu Applicant's institution: ANL Applicant's division: Materials Science Project Name: Theory Project title: Development and Application of Accurate Theoretical Models for Calculating the Thermodynamics of Chemical Bonds for Heterogeneous Catalysis Associated funding: Postdoctoral Director’s Fellowship at Argonne Other Systems: Science: The decline of fossil fuels dependency of the US on foreign sources, has led to the exploration of utilizing alternative carbon resources, such as CO2 (as a product of fossil fuel combustion and as a greenhouse gas) and lignin (as a sustainable and high-energy content biomass). Novel and efficient catalytic processes are an essential technology for realizing the chemical transformations of these feedstocks into fuels. A number of studies on homogeneous catalysis have helped to understand the chemical and mechanistic insights of the reactions. However, heterogeneous catalysis that supports the majority of industrial processes often lacks these insights; the innate complexity of heterogeneous catalysts (e.g., metal/metal oxide surfaces, metal clusters and nanoparticles, etc.) provide great challenges for not only experimentalists but also computational scientists to investigate the chemical insights behind the catalytic reactions. Developing accurate a nd time-efficient computational methods/approaches to help better understand heterogeneous catalysis can have great contribution to rational design of catalysts that can ultimately lead to novel industrial processes. Catalytic transformation of carbon feedstocks often involves a) Activation of a polar bond, e.g., C-O bond cleavage, and b) Hydrogenation, e.g., C-H or O-H bond formation. Transition metal catalysts have been most widely used in this kind of catalysis because of their efficient properties on bond activation and formation. Metal centers are the most important reaction media and the keys to unlock chemical insights of the reactions. For instance, transition metal mediated hydrogenation first goes through an H-H bond cleavage of H2 to form an M-H bond (M = transition metal). Then the M-H bond is broken to release hydrogen (H+, H−or H•), which is used for hydrogenation to form C-H or O-H bond. The stability and the thermodynamic properties of these polar bonds, especially the M-H bond, determine the reaction barriers of the hydrogenation, which ultimately reflect the catalytic properties of the catalyst. Therefore, the accurate prediction of thermodynamic properties of a chemical bond will provide important information about the catalyst candidates and help guide catalyst design. In this study, we propose a theoretical protocol for calculating heterogeneous M-H heterolytic cleavage energy in water as an example (eq. 1). Because the evaluation of ΔG in eq. 1 requires sampling of the reverse process, the protonation of the base M- surrounded by its equilibrium hydration shell (i.e., inserting a proton into a condensed MD model system) is more challenging and costly than increasing the electron count. Thus, this problem can be worked around by introducing two reaction energy terms, the formation energy of a gas phase proton, ΔfGH+(g) (eq. 2), and the solvation energy of a proton, ΔSGH+ (eq. 3), both of which have been determined experimentally. In the following we can calculate the ionization potential of the metal (ΔIPGM-(aq), eq. 4), as well as the reaction energy of hydrogen production from M-H (ΔfGH2(g), eq. 5). In eq. 4 the electron is completely eliminated from the MD model system. To balance the oxidation reaction we can consider it as placed in a vacuum reservoir (vac) where all thermodynamic energies are by definition zero. The vac state is actually the reference state used for electrons in electrochemistry. Then we have eq. (1) = (2) + (3) ̶ (4) + (5), thus the target reaction energy ΔG = ΔfGH+(g) + ΔSGH+ ̶ ΔIPGM-(aq) + ΔfGH2(g). M-H (aq) → M- (aq) + H+ (aq) ΔG (1) ½ H2 (g) → e- (vac) + H+ (g) ΔfGH+(g) (2) H+ (g) → H+ (aq) ΔSGH+ (3) M- (aq) → M (aq) + e- (vac) ΔIPGM-(aq) (4) M-H (aq) → M (aq) + ½ H2 (aq) ΔfGH2(g) (5) In practice, the lower the ΔG, the more easily the catalyst would produce H+. Also, other thermodynamic descriptors such as pKa can be calculated based on ΔG’s. Thus this approach can be used to screen different transition metal catalysts to determine the best candidate that produces H+ for hydrogenation. For instance, systematic studies can be carried out on SiO2 embedded single metal atom catalysts (currently being developed in Larry Curtiss group), to investigate the intrinsic catalytic properties of different transition metal centers. On the other hand, similar approaches can be developed on M-H bond cleavage to H- and homolytic M-H cleavage to produce H•, as well as other important chemical bonds in a catalysis process. Project description: Structure optimizations and energy calculations of selected metal and metal hydride surfaces (~45 atoms) and H2 will be carried out using density functional theory (DFT) calculations within VASP package. The metal surfaces will be periodic systems, thus plane wave basis sets will be utilized. At the same time, molecular homogeneous models will also be considered to compare with heterogeneous systems. Therefore, Gaussian 09 will be used to perform DFT and high level ab initio calculations for accurate reaction energies. Both VASP and Gaussian 09 programs are currently available on Fusion cluster and scale reasonably well on parallel processors. Project URL: Requested allocation: 480000 Q1: 120000 Q2: 120000 Q3: 120000 Q4: 120000 Justification: The requester has used undetermined amount hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System