Multi-Scale Molecular Dynamics Simulation of Self Assembling Nanoparticles |
|
Materials:
Nanomaterials
Semiconductors
Organic
Application: Nanotechnology Electronic Technique: Computation |
|
We are investigating the “bottom-up” design of novel molecular nano-electronic structures via a multi-scale computer simulation method that includes ab initio quantum mechanical calculations, molecular dynamics simulations with classical and reactive force fields, monte carlo simulations and mesoscale simulations. Our approach to the design of these molecular nanostructures is based on the self-assembly of functionalized molecular building blocks, which will allow for optimization of the electronic, thermal and mechanical properties of these self-assembled structures.<br> We are currently concentrating on using POSS (Polyhedral Oligomeric Silsesquioxane) molecules that feature by a cage shaped inorganic core molecule, SiO1.5, as nano building blocks to design novel molecular structures. POSS molecules have been found to be ideal molecular nano bulding blocks with flexible functionality and the ability to enhance mechanical and thermal properties when added to polymers. Furthermore, the T8-POSS molecules have a unique cubic molecular shape that implies very ordered self-assembled structures.<br> In our recent work, the thermal, mechanical, vibrational and structural properties of these functionalized POSS building blocks are first explored in ab initio calculations and molecular dynamics simulations. Results from the simulations are compared with existing experimental works to verify that the simulation methods correlate to the system we are studying. After the validation, a series of functionalized POSS molecular systems were simulated. One of the interesting results indicates that POSS cages in the crystals form always have a unique rhombohedra packing. This suggests possible parallel packing also exists for POSS functionalized molecules in crystal form. Paralleled packing is desirable from the standpoint of small molecule organic semiconductors because it means enhancements in the ? orbital overlapping and thus possible higher charge carrier mobility. As the acene molecules are always packed in crystal form as a herringbone fashion, we functionalized acene with POSS to effect a parallel packed acene molecule schema in the crystal structures. Ab initio quantum mechanical calculations and molecular dynamics simulations were performed to characterize the individual electronic properties of these functionalized POSS molecules to find molecules with promise as nano-electronic formers. Those molecules were chosen for the packing prediction study. The predicted polymorphs of these novel structures then were further relaxed by ab initio calculations to allow for accurate structural data that could be compared to actual experimental work. These procedures are performed iteratively until the optimized nano-structures are found. Finally, electronic properties, expressed as band structures, of these crystal polymorphs were evaluated in ab initio calculations while the thermal and mechanical properties are evaluated in molecular dynamics simulations. <br>Our simulations reveal that these acene molecules functionalized POSS configurations do have parallel packing crystal polymorphs, and thus, these materials may exhibit higher charge carrier mobility. Electronic properties evaluations from the new molecules showed similar band gaps than pure acene molecules, but the bulk materials have superior thermal and mechanical bulk properties. Hence, these novel functionalized POSS oligomers are potential new candidates for semi-conducting organic/inorganic hybrid molecular materials. The goal of our work is to advance the design and synthesis of new materials by exploring and strengthening the efficacy of a building block based nano scale self-assembly approach. |
Skip to content.
Skip to navigation
