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Robert J. Gdanitz NC A&T State University

Very large-scale computations of the free energies of eight low-lying structures of arginine in the gas phase. Robert J. Gdanitz NC A&T State University. 5 canonical (neutral) and 3 zwitterionic structures. C1. C2. C3. C4. C5. Z1. Z2. Z3. C1. C2. C3. C4. C5. Z1. Z2. Z3.

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Robert J. Gdanitz NC A&T State University

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  1. Very large-scale computations of the free energies of eight low-lying structures of arginine in the gas phase Robert J. Gdanitz NC A&T State University

  2. 5 canonical (neutral) and 3 zwitterionic structures C1 C2 C3 C4 C5 Z1 Z2 Z3

  3. C1 C2

  4. C3 C4

  5. C5 Z1

  6. Z2 Z3

  7. Theory Electronic Schrödinger equation: Hamiltonian: Constraint #1: Spin symmetry Constraint #2: Pauli principle:

  8. Algebraization “Configuration Interaction” (CI): Slater determinants: Orbitals:

  9. Approximation Basisset full-CI

  10. Approximation of full-CI Perturbation theory: Coupled-Cluster:

  11. Extrapolation to basis set limit Independent particle contribution: Singlet pairs: Triplet pairs:

  12. NWMpp1: 512-node IBM SP (retired) Computers & Software (PNNL) NWMpp2: 1960-processor HP/Linux NWChem, PNNL MP2/QZ and CCSD(T)/DZ: 128 proc./48 GBytes of NWMpp1 for 2 days

  13. Energy w/r/t C5

  14. The Winners C5 DG = 0.4 kcal/mol C3

  15. Thanks Wim Cardoen, Utah Robert Harrison, Oak Ridge Nat’l Lab Bert de Jong, PNNL Anita Orendt, Utah Jack Simons, Utah Piotr Skurski, Gdansk, Poland Theresa Windus, PNNL

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