Accelerated First-Principles Exploration of Structure and Reactivity in Graphene Oxide

Graphene oxide (GO) materials are widely studied, and yet their atomic-scale structures remain to be fully understood. Here we show that the chemical and configurational space of GO can be rapidly explored by advanced machine-learning methods, combining on-the-fly acceleration for first-principles molecular dynamics with message-passing neural-network potentials. The first step allows for the rapid sampling of chemical structures with very little prior knowledge required; the second step affords state-of-the-art accuracy and predictive power. We apply the method to the thermal reduction of GO, which we describe in a realistic (ten-nanometre scale) structural model. Our simulations are consistent with recent experimental findings and help to rationalise them in atomistic and mechanistic detail. More generally, our work provides a platform for routine, accurate, and predictive simulations of diverse carbonaceous materials

Preserving Charge and Oxidation State of Au(III) Ions in an Agent-Functionalized Nanocrystal Model System

Supporting functional molecules on crystal facets is an established technique in nanotechnology. To preserve the original activity of ionic metallorganic agents on a supporting template, conservation of the charge and oxidation state of, the active center is indispensable. We. present a model system of a metallorganic agent that, indeed, fulfills this design criterion on a technologically relevant metal support With potential Impact on Au(III)-porphyrin-functionalized nanoparticles for an improved anticancer-drug delivery. Employing scanning tunneling microscopy and -spectroscopy in combination with photoemission spectroscopy,we clarify at the single-molecule level the underlying mechanisms of this exceptional adsorption mode. It is based on the balance between a high-energy oxidation state and an electrostatic screening-response of the surface (image charge). Modeling with first principles methods reveals submolecular details of the metal-ligand bonding interaction and completes the study by providing an Illustrative electrostatic.. model relevant for ionic metalorganic agent molecules, in general

Computational Study of Structures and Electronic Properties of Metal Clusters

Subnanometer sized transition metal clusters have attracted a great deal of interest in recent years. In this thesis we have investigated the structures, electronic and optical properties, the structural evolution due to doping with a heteroatom, and the catalytic activity of subnanometer sized Aun (n = 2-20) clusters using various computational methods. Another major theme of this thesis has been to understand the mechanisms of organic reactions such as C–C coupling and cycloisomerization reactions triggered by transition metal complexes. We have reported electronic and chemical properties of novel 2D materials such as fluorographene, germanene, and germanane. One future extension of this work shall be the investigation of metal clusters anchored on these 2D systems for designing heterogeneous catalysts for vital organic transformations, which has been studied in the presence of naked metal clusters and metal complexes in the present thesis.Research was carried out under the supervision of Prof. Ayan Dutta of Spectroscopy division under SPS [School of Physical Sciences]Research was conducted under IACS fellowship and DST gran

Pattern Formation Due to Fluorination on Graphene Fragments: Structures, Hopping Behavior, and Magnetic Properties

Structures and mechanism of pattern formation for the radical fluorination on selected polyaromatic hydrocarbons (PAH) has been studied using density functional theory (DFT) methods. Our study reveals that the F• radical addition occurs preferentially at the edges of PAHs followed by the hopping of F• to the center due to the fluxional nature of C–F bond. F• migrates preferentially over the C–C bonds having a lower barrier than that over the aromatic π-cloud in cases of monofluorinated PAHs. Addition of a second F radical can stabilize the system, cooperatively. When two F• are added to the adjacent C atoms, it forms the minimum energy patterns. However, the addition of two fluorine radicals at the meta position of the same aromatic ring would lead to the stabilization of the triplet state compared to the singlet ground state. Therefore, depending on the sites of F• addition, these structures exhibit ferromagnetic/antiferromagnetic ground states. Considering the low barrier heights for the F• hopping, these systems are predicted to be in a dynamic equilibrium with their less stable ferromagnetic states. Our study also provides an atomistic understanding of the well-known rate determining state for the fluorine pattern formation in graphene and CNT

Mechanistic insights into the synergistic catalysis by Au(<scp>i</scp>), Ga(<scp>iii</scp>), and counterions in the Nakamura reaction

DFT calculations explain the origin of Au/Ga dual catalyzed regioselectivity of Nakamura reactions. The role of the counterions and the triazole ligand is shown to be significant.</p