Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Alvaro VazquezMayagoitia Applicant's institution: ANL Applicant's division: LCF Project Name: tsvdw_nwchem Project title: Implementation and validation of TS van der Waals contribution in NWCHEM Associated funding: Other Systems: Intrepid, Surveyor (1M) Science: The molecular interactions are the product of several contributions, attractive or repulsive. In weak interactions the dispersion energies are the main responsible of middle range attractions. Density Functional Theory (DFT), the most used ab initio method in material science, cannot describe appropriately multipolar energy contributions; particularly, the description of dispersion energies is one of its mayor problems. A way to take in account the dispersion energies in Generalized Gradient Approximation functionals (GGA) is by adding a correction term to the total DFT energy. This dispersion energy contribution is often evaluated by empirical methods parametrized to reproduce experimental energies or benchmark databases, nevertheless those empirical parameters may not be universal or may not be considering properly new systems. We propose to add to the ab initio code NWCHEM a parameter-free model to the dispersion energy based on atoms-in-molecules scheme. Project description: The model will use to correct dispersion energies is based on the scheme proposed by Tkatchenko-Scheffler (PRL, 102, 073005,2009), which represents the dispersion energy contribution as the sum of pairwise atoms interactions. The atoms interaction of the atoms A and B are represented by C6/R^6, where R is the distance between both atoms, and C6 is the average of the dispersion coefficients of A and B scaled by the proportion of their Hirshfeld volumes. We are implementing the TS in the quantum chemistry suite NWCHEM, and we pretend evaluate a long series of interacting molecules to validate this new model in the code. The systems to be evaluated are: the benchmark data base S66, S22, JSCH and HBC6. (see JCP, 134, 084107,2011). NWChem has been installed in Fusion and other computing facilities. NWChem was designed to execute in parallel with excellent scalability for some hundreds of processors. Project URL: Requested allocation: 150000 Q1: 90000 Q2: 20000 Q3: 20000 Q4: 20000 Justification: The requester has used undetermined amount hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System