Tuning the Dirac Cone of Bilayer and Bulk Structure Graphene by Intercalating First Row Transition Metals using First Principles Calculations

Modern nanoscience has focused on two-dimensional (2D) layer structure materials which have garnered tremendous attention due to their unique physical, chemical and electronic properties since the discovery of graphene in 2004. Recent advancement in graphene nanotechnology opens a new avenue of creating 2D bilayer graphene (BLG) intercalates. Using first-principles DFT techniques, we have designed 20 new materials \textit{in-silico} by intercalating first row transition metals (TMs) with BLG, i.e. 10 layered structure and 10 bulk crystal structures of TM intercalated in BLG. We investigated the equilibrium structure and electronic properties of layered and bulk structure BLG intercalated with first row TMs (Sc-Zn). The present DFT calculations show that the 2$p_z$ sub-shells of C atoms in graphene and the 3$d_{yz}$ sub-shells of the TM atoms provide the electron density near the Fermi level controlling the material properties of the BLG-intercalated materials. This article highlights how the Dirac point moves in both the BLG and bulk-BLG given a different TM intercalated materials. The implications of controllable electronic structure and properties of intercalated BLG-TM for future device applications are discussed. This work opens up new avenues for the efficient production of two-dimensional and three-dimensional carbon-based intercalated materials with promising future applications in nanomaterial science.Comment: 60 pages, 9 figures. arXiv admin note: text overlap with arXiv:1701.03936 by other author

Iron Intercalation in Covalent-Organic Frameworks: A Promising Approach for Semiconductors

Covalent-organic frameworks (COFs) are intriguing platforms for designing functional molecular materials. Here, we present a computational study based on van der Waals dispersion-corrected hybrid density functional theory (DFT-D) to design boroxine-linked and triazine-linked COFs intercalated with Fe. Keeping the original $P-6m2$ symmetry of the pristine COF (COF-Fe-0), we have computationally designed seven new COFs by intercalating Fe atoms between two organic layers. The equilibrium structures and electronic properties of both the pristine and Fe-intercalated COF materials are investigated here. We predict that the electronic properties of COFs can be fine tuned by adding Fe atoms between two organic layers in their structures. Our calculations show that these new intercalated-COFs are promising semiconductors. The effect of Fe atoms on the electronic band structures and density of states (DOSs) has also been investigated using the aforementioned DFT-D method. The contribution of the $d$-subshell electron density of the Fe atoms plays an important role in improving the semiconductor properties of these new materials. These intercalated-COFs provide a new strategy to create semi-conducting materials within a rigid porous network in a highly controlled and predictable manner.Comment: 39 pages. arXiv admin note: text overlap with arXiv:1703.0261

MultiBinding Sites United in Covalent-Organic Frameworks (MSUCOF) for H2_2 Storage and Delivery at Room Temperature

The storage of hydrogen gas (H$_2$) has presented a significant challenge that has hindered its use as a fuel source for transportation. To meet the Department of Energy's ambitious goals of achieving $50$ g L$^{-1}$ volumetric and $6.5$ wt \% gravimetric uptake targets, materials-based approaches are essential. Designing materials that can efficiently store hydrogen gas requires careful tuning of the interactions between the gaseous H$_2$ and the surface of the material. Metal-Organic Frameworks (MOFs) and Covalent-Organic Frameworks (COFs) have emerged as promising materials due to their exceptionally high surface areas and tunable structures that can improve gas-framework interactions. However, weak binding enthalpies have limited the success of many current candidates, which fail to achieve even $10$ g L$^{-1}$ volumetric uptake at ambient temperatures. To overcome this challenge, We utilized quantum mechanical (QM) based force fields (FF) to investigate the uptake and binding enthalpies of 3 linkers chelated with 7 different transition metals (TM), including both precious metals (Pd and Pt) and first row TM (Co, Cu, Fe, Ni, Mn), to design 24 different COFs in-silico. By applying QM-based FF with grand canonical Monte Carlo (GCMC) from 0-700 bar and 298 K, We demonstrated that Co-, Ni-, Mn-, Fe-, Pd-, and Pt-based MSUCOFs can already achieve the Department of Energy's hydrogen storage targets for 2025. Surprisingly, the COFs that incorporated the more affordable and abundant first-row TM often outperformed the precious metals. This promising development brings us one step closer to realizing a hydrogen-based energy economy

Inteligencia y contrainteligencia militar frente a fallos y desafíos. El caso de Culiacán, México (2019)

  This analysis is based on the dissertation The Mexican Army decision-making process: The role of Military Intelligence. The original research is applied to the case of the Ovidio Guzmán capture operation in Culiacán, Sinaloa, Mexico. First-hand sources of military intelligence are confronted with information from open sources to evaluate the possible intelligence and counterintelligence failures that can explain the Mexican government´s decision to release Ovidio Guzman after members of his cartel committed acts of extreme violence and exploited social media. Based on the sources consulted, the author concludes the key factors that led to the failure of the operation were the lack of inter-agency cooperation and deficiencies in the decision-making process by the Security Cabinet of Mexico.El presente artículo se deriva de la tesis doctoral El proceso de toma de decisiones en el Ejército Mexicano: la función de la Inteligencia Militar. La investigación es retomada para analizar la operación de captura de Ovidio Guzmán, en Culiacán, Sinaloa, México. Se confrontan fuentes de primera mano de inteligencia militar con información de fuentes abiertas y se determinan los posibles fallos de inteligencia y contrainteligencia que condujeron al gobierno mexicano a tomar la decisión de liberar a Ovidio Guzmán frente a los actos de violencia y al uso del ciberespacio por el crimen organizado para tal fin. A partir de la información consultada, se concluye que existió una falta de cooperación interagencial y fallos del Gabinete de Seguridad de México en el proceso de toma de decisiones en situaciones críticas. Abstract This analysis is based on the dissertation The Mexican Army decision-making process: The role of Military Intelligence. The original research is applied to the case of the Ovidio Guzmán capture operation in Culiacán, Sinaloa, Mexico. First-hand sources of military intelligence are confronted with information from open sources to evaluate the possible intelligence and counterintelligence failures that can explain the Mexican government´s decision to release Ovidio Guzman after members of his cartel committed acts of extreme violence and exploited social media. Based on the sources consulted, the author concludes the key factors that led to the failure of the operation were the lack of inter-agency cooperation and deficiencies in the decision-making process by the Security Cabinet of Mexico

Band Motor Crankshaft for Hydrogen Combustion Engine

This report outlines the steps in which a group of four mechanical engineers at California Polytechnic State University California, San Luis Obispo, addressed an issue brought up by Professor Roger Benham from the Materials Department. The task included developing an automated and modular testing platform for a revolutionary concept crankshaft prototype – meant for a hydrogen combustion engine - developed and produced by the sponsor: Roger Benham. A testing platform is necessary to measure the performance of the shaft design created to eventually implement this subsystem into a complete hydrogen engine design. Values being tested include geometric validation, maximum static loading, maximum dynamic loading, and fatigue testing – these values are calculated via a physical strain gauge on the shaft and a separate Microsoft Excel calculator for validation. Throughout this process, we have implemented the standard engineering design process along with its corresponding reports alongside other specific techniques such as finite element analysis and material design analysis. Overall, the team was able to successfully build an automated test platform that loaded the crankshaft but fell short on the load requirements. Although desired motion was achieved, our system fell short of all load requirements. The system did not put enough torque onto the shaft for our strain gauges to pick up any deflection or torsion. Consequently, no stress values were able to be read. In summary, our team was able to successfully implement an automated and modular design that adequately simulates the desired motion of the crankshaft but fails to output stress values due to lack of torque

Exploring Low Internal Reorganization Energies for Silicene Nanoclusters

High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we performed DFT calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n-type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the zigzag and armchair directions may permit the design of novel n-type electronic materials and spinctronics devices that incorporate both high electron affinities and very low internal reorganization energies.Comment: 25 pages, 6 figure