Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Handan Yildirim Project Name: md_pls_dft_for_TiO2 Division: CNM Project title: First Principles and Classical Molecular Dynamics Calculations of Lithium Intercalation into TiO2 Surfaces and Nanostructures Associated funding: BES Other Systems: Carbon 150 000 Science: First principles calculations based on Density Functional Theory (DFT) and classical Molecular Dynamic (MD) simulations (using polarizable potentials) will be performed to study diffusion and intercalation of Li in TiO2 crystalline and amorphous nanoparticles and nanotubes of several sizes. These simulations are directly relevant to the exploration of the properties of titania as an alternative electrode for energy storage for Li ion batteries. Our calculations will be the extension of our earlier study at which Li diffusion and intercalation characteristics are derived for bulk TiO2 polymorphs. The effect of Li concentration on the diffusion energetics and dynamics in the nanostructures will be studied for better understanding of their electrochemical performance. We will compare our results obtained those for the bulk anatase, rutile and amorphous TiO2 to extract the role of nanostructuring and morphology on the diffusivity of Li ions. Additionally, the structural transitions upon certain concentration of Li intercalation into these structures will be evaluated, and compared to that observed in the amorphous TiO2. We will also extend our study to explore pressure-induced structural transitions and role of nanostructuring on the transition pressure. The present study requires detailed analysis of the energetics, dynamics of Li in TiO2 under various concentration and temperature conditions. For these calculations, we will vastly benefit from the ability of classical MD simulations that allow simulation of several thousands of atoms. We will explore the size effects on Li intercalation properties. We will use MD simulations (for temperatures ranging form 300K to 900K) for a long enough time (~ 5ns at the current studies) to explore the details of the Li diffusion mechanisms in both crystalline and amorphous TiO2 nanoparticles and nanotubes for concentrations ranging from 25% to 100%. The observed mechanisms of diffusion will be supplie d as an input to calculate the corresponding energetics and dynamics using periodic Density Functional Theory calculations. Project description: In our preliminary simulations, we have obtained insights into the diffusivity of Li in the TiO2 polymorphs including amorphous (bulk) and nanostructures. The concentration effect, mechanisms for diffusion in different polymorphs, and host morphology effects on the diffusivity of Li ions are explored by comparing the results obtained for anatase, rutile and amorphous bulk TiO2 and anatase and amorphous nanostructures. The structural as a function of Li concentration are studied extensively. The structural properties and the diffusivity of Li ions in the new crystal phase are explored in details. The results of MD simulations at relatively low temperatures are analyzed to identify Li diffusion mechanisms in these systems, and the obtained mechanism is used to calculate the corresponding isolated Li diffusion energetics using DFT. Our MD results, in summary, showed that Li ions diffuse with different mechanism at each system that is mostly determined by the host lattice structure. We could also trace clearly the effect induced by nanostructuring on the diffusivity of Li ions. We performed classical MD simulations to study Li diffusion energetics and dynamics under several conditions using the DL-POLY code. We have gained significant insights into the role of concentration and morphology on the diffusivity of Li ions in the bulk TiO2 polymorphs. Additionally, phase transition with high Li load and under certain pressure range is observed with these studied for nanosecond time scales. These simulations are indeed computationally intensive as the systems have large number of atoms. Our calculations for this part of the study are performed with a very fine time step (~0.2 fs in general), requiring long simulation hours even for 5ns (due to the type of the potential used). For the calculations of nearly 5000 to 10000 atoms for simulating 5ns, 25 to 50 millions simulation steps are needed. As our simulations extend to several temperature and concentration ranges, the need for intensive computational time can be understood. For the proposed project on nanoparticles and tubes, we have tested the reliability of the potential by studying different sizes of nanoparticles ranging from 2nm to 10nm. The detailed structural analysis and the diffusivity are explored for each Li concentration in the small nanoparticles up to 6nm. Concentration dependent diffusivity profile of Li ions are extracted and compared to those obtained for bulk TiO2. We now would like to extend these simulations and test the diffusivity profile and structural transitions for larger nanoparticles particularly for disordered nanoparticles, and those particles under pressure. Each simulation will be conducted for at least 1 ns and expected not to exceed 5ns. As the size of the particles are fairly large, significant computational resources are needed. For instance, in order to complete the calculations for 6nm nanoparticle for 5 concentrations and 6 temperatures, we required of about 80,000 cpu hours. We anticipate that we will be r unning of about 10 to 15 jobs per day to complete the proposed research. Project URL: Current FY Hours Used: undetermined amount New FY Requested allocation: 400 Q1: 150 Q2: 150 Q3: 50 Q4: 50 Justification: Thank You, The LCRC Accounts System