NWChem is computational chemistry package for the study of large chemical systems that is under development and is designed to run on high-performance parallel supercomputers as well as workstation clusters. It aims to be scalable both in the ability to treat large problems efficiently, and in its usage of available parallel computing resources. The suite utilizes parallel programming tools (TCGMSG and the Global Array library) developed by PNNL staff. NWChem has been optimized to perform calculations on large molecules using large parallel computers; the code has been ported to the following MPPs: KSR-1/2, Intel Delta/Paragon, CRAY T3D and IBM SP1/2.
Current functionality includes:
Quantum Chemical study of the binding of alkali metal cations with crown-ethers: effects of computational parameters and methods.
Crown ethers have drawn much experimental and theoretical interest
since they were first described by Pederson in 1967. These cyclic
polyethers show a remarkable range of specificity for metal cations
and are being considered as separation agents for radioactive cations
in waste steams. As a prototypical interaction of these systems we
have studied the binding of various alkali metal cations with multiple
crown ether derivatives using Local and Non-Local DFT and MP2 methods.
Binding energies for these system have been determined from moieties
whose structures have been optimized using a variety of approximations
within the DFT method, including: various basis sets (orbital and
charge density fitting), numerical grids (various levels of accuracy,
and types), and basis set superposition errors (orbital and grid).
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