Download or read book Understanding and Designing Complex Potential Energy Landscapes Across the Nanoscale written by Yan Yang and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, I will discuss four projects I participated during my Ph.D. study, with an emphasis on understanding and designing complex energy landscape between molecules and materials across nanoscale. These research projects are organized into four chapters: Chapter 1: Designer Potential Energy Surfaces via Programmable Magnetic Interactions; Chapter 2: Influence of Pore Size on the van der Waals Interaction in Two-Dimensional Molecules and Materials; Chapter 3: Non-Additivity and Finite-Size Effects in the Polarizabilities and Dispersion Coefficients of the Fullerenes; Chapter 4: Competitive Adsorption as a Route to Area-Selective Deposition. In Chapter 1, we explore how programmable magnetostatic interactions can be used in the rational design of Potential Energy Surfaces (PES) with targeted features. We first explore the PES design space that is accessible with small patterned magnetic arrays via forward and exhaustive enumeration, and characterize the resulting PES by the number, locations, and depths of the PES critical points. This is followed by a detailed investigation into the inverse problem-identification of magnetic patterns that correspond to PES with predefined features-using simulated annealing Monte Carlo (SA-MC) methods. In doing so, we demonstrate a robust theoretical and conceptual paradigm that enables forward and inverse PES engineering with precise control over the critical points and other salient surface features, thereby paving the way towards directed self-assembly using programmable magnetic interactions. As the magnetic interactions are scale-invariant, this approach can essentially scale down to the nanoscale. In Chapter 2, we investigate the influence of void space in porous twodimensional (2D) molecules and materials systems to the van der Waals (vdW) scaling landscape [1]. Analytical and numerical models presented herein demonstrate that the mere presence of a pore leads to markedly different vdW scaling across non-asymptotic distances, with certain relative pore sizes yielding effective power laws ranging from simple monotonic decay to the formation of minima, extended plateaus, and even maxima. These models are in remarkable agreement with first-principles approaches for the 2D building blocks of covalent organic frameworks (COFs), and reveal that COF macrocycle dimers and periodic bilayers exhibit unique vdW scaling behavior that is quite distinct from their non-porous analogs. These findings extend across a range of distances relevant to the nanoscale, and represent a hitherto unexplored avenue towards governing the self-assembly of complex nanostructures from porous 2D molecules and materials. In Chapter 3, we explore the nonadditivity and finite-size effect in a series of popular fullerene molecules [2]. We compute the static isotropic polarizability series (l with l = 1, 2, 3) for the C60-C84 fullerenes using finite-field derivative techniques and density functional theory (DFT), and quantitatively assess the intrinsic non-additivity in these fundamental response properties. By comparing against classical models of the fullerenes as conducting spherical shells (or solid spheres) of uniform electron density, a detailed critical analysis of the derived effective scaling laws (α1~ N^1.2, α2~N^2.0, α3~N^2.7) demonstrates that the electronic structure of finite-sized fullerenes-a unique dichotomy of electron confinement and delocalization effects due to their quasispherical cage-like structures and encapsulated void spaces-simultaneously limits and enhances their quantum mechanical response to electric field perturbations. Corresponding frequency-dependent polarizabilities are obtained by inputting the ` series into the hollow sphere model (within the modified single frequency approximation), and used to compute the molecular dispersion coefficients (Cn with n = 6, 8, 9, 10) need to describe the non-trivial vdW interactions in fullerene-based systems. Using first-order perturbation theory in conjuction with >140,000 DFT calculations, we also computed the non-negligible zero-point vibrational contributions to a1 in C60 and C70, thereby enabling a more accurate and direct comparison between theory and experiment for these quintessential nanostructures. In Chapter 4, we explore the use of competitive adsorption to facilitate area-selective deposition (ASD) [3,4]. ASD has the potential to enable next-generation manufacturing and patterning at the 5 nm node and beyond, with direct energy-related applications in solar cells, batteries, fuel cells, supercapacitors, catalysts, and sensors. Well-known for its ability to deposit atomically thin films with Angstrom scale precision along the growth direction and conformally over complex 3D substrates, ALD has already emerged as a key process in nanomanufacturing. In this regard, the range and scope of ALD-based applications and capabilities can be substantially extended by also controlling the in-plane growth, a timely and significant development that can be realized via ASD processes that depend on the chemical composition of the underlying surface. In this joint theoretical-experimental work (with the Engstrom Group at Cornell), competitive adsorption strategies will be leveraged to enable AS-ALD by blocking the dissociative chemisorption of the metal-containing precursor. In this approach, the co-adsorbate must differentiate between two competing surfaces by binding more strongly to one over the other. We computationally identified a series of co-adsorbates that can induce selectivity during chemical vapor deposition (CVD) and ALD process using dispersion-inclusive DFT, and used two of these co-adsorbates to achieve a deposition of ~30nm of a thin film on the desired growth surface using AS-CVD and 1.5nm using AS-ALD.