Granted 90k - JB On Wed, Nov 25, 2015 at 11:37 AM, [email protected] <[email protected]> wrote:

Hello,

A change in allocation has been requested:

Requester: verdicm (Marco Verdicchio) Project: LowF_VRC-TST Title: Low frequencies modes coupling in Variable Reaction Coordinate TST Description: - Computational methods:

We intend to use VRC-TST theory to study the effect of coupled low frequencies motions on EJ-resolved, microcanonical and canonical kinetic constants for several radical-radical association reactions. The central focus of VRC-TST is the evaluation of the reactive flux through an arbitrary dividing surface for several temperatures. In particular a multifaceted dividing surface approach, which allow for the incorporation of multiple dividing surfaces for each binding site, will be adopted. This scheme allows high flexibility on the dividing surface shape and the possibility to take into account additional reaction pathways (i.e. H atom abstraction). Unfortunately the computational cost of each kinetic calculation increases with the number of considered dividing surfaces. A variational minimization of the reactive flux is then performed with respect to both the location of the pivot points and the distances between them.

The previous allocation let us to investigate the low-frequencies effect on the rate constants for several systems:

- CH3 + H - CH3 + CH3 - CH2CH3 + H - CH2CH3 + CH3 - H +C2H3

with excellent results.

The Blues machine has been found to be of great help for this type of studies allowing us to use a large number of processors (128 cpu for an average of 24h per job) and speed up considerably our calculations.

In this third stage of the project, we would like to move our attention to different systems like: - CH3 + CH2OH - H + CH2OH These systems, in fact, have been already investigated within the previous allocation, but the complexity of their potential energy surface require additional work in order to work out an accurate rate constant (the low-freq effect has a strong dependence on the potential energy surface). Moreover the extension of this method to oxygenated systems: - O2 + CH3 - O2 + CH2CH3 requires the use of high level ab initio calculations (because of the presence of the O2 molecule) which are highly computationally demanding.

- Technical details:

Kinetic calculations will be performed using the VRC-TST method as implemented in the computer code VaReCoF (Y. Georgievskii, S.J. Klippenstein, VaReCoF, Sandia National Laboratories and Argonne National Laboratory, 2006). The code makes use of the MOLPRO or GAUSSIAN quantum chemistry software for on-the-fly evaluation of the potential energy. A Python interface to the code has been implemented for the management of the input files (reference energy evaluation, pivot points positions, etc.), for the generation of the input different structures ([Phi,Chi] grid of points) and for results post processing.

The code does not require large amount of memory (less than 1GB) and works very efficiently on parallel architectures. The code makes use of MPI and shows a speed-up efficiency of about 60% for up to 96 CPU’s (test performed on a 8 cpu/cores AMD Operton 2354 machine). Improvement is expected with better CPUs and fastest internode connections.

- Expected number of project members:1

Current: undetermined amount Justification:

Requested: 90000

A specific reason has been given: Development of analytical potential energy surfaces for the investigated systems.

The code for the calculation of the abinitio points has been already developed and tested, with great results, within previous allocation.

This needs to be approved and the final allocation amount decided upon.

Thank You, The LCRC Accounts System