Hello, A change in allocation has been requested: Requester: zapol (Peter Zapol) Project: glassforms Title: First-principles Calculations of Mineral and Glass Dissolution under Various pH Conditions Description: The first task for this year is to extend our study from simple sodium borosilicate glass to a model model glass with other constituting elements. In the past year, we have calculated hydrolysis reaction barriers of the Si-O-B bridges and the B-O-B bridges at surface sites of sodium borosilicate glass as a model system in different protonation states – neutral (≡SiOH), protonated (≡SiOH2+) and deprotonated (≡SiO-) using the Nudged Elastic Band (NEB) method. As there are other constituting elements, e.g. Al, in waste glasses, we will calculate the reaction barriers of T-O-T bridges (T=Si, Al, B) at surface sites in different protonation states – neutral (≡SiOH), protonated (≡SiOH2+) and deprotonated (≡SiO-) using the Nudged Elastic Band (NEB) method by using VASP code. The second part is studies of the bulk water effect to determine the role of aqueous solution and the entropic effect of water. Both effects contribute to the free energy reaction barriers. In this year, we will perform MD simulations to study the dissolution process of glass with Si and other constituting elements under acidic, neutral and basic conditions by using VASP and CPMD codes. Current: undetermined amount Justification: The first-principles calculations will be carried out using the electronic-structure code VASP. In the first part, NEB calculations will be performed to calculate the reaction pathways for a variety of composing elements under acidic, neutral and basic conditions. A single geometry optimization takes 48 hours on 32 processors. We are considering 30 supercell samplings of silicate glasses including multiple T sites (Si, Al, B). The calculation for possible reactants, intermediates, products will take about 140,000 core hours. It takes about 50 hours on 160 processors (5 images) to calculate a reaction barrier along the reaction pathway. The total estimated computer time for barrier calculation is 240,000 core hours. In the second part, ab initio MD simulations will be performed, where each trajectory runs for 100 ps and it takes 32 processors to run for 96-160 hours (average 2048 core hours per trajectory). We will need to run 100 trajectories for five sets of calculations. That requires 400,000 core hours. In sum, the total requested allocation for this project is 780,000 core hours. Requested: 200000 A specific reason has been given: We have used all allocated time productively and we need to run additional calculations. This needs to be approved and the final allocation amount decided upon. Thank You, The LCRC Accounts System