this talk has only three equations

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Group meeting in group retreat in Puerto Rico

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this talk has only three equations

  1. 1. this talk has only three equations Jiahao Chen Vieques, PR http://mfrost.typepad.com/cute_overload/2006/05/bullblob.html
  2. 2. qtpie: how cute can you get? http://mfrost.typepad.com/cute_overload/2006/02/peeky_mcpeekers.html
  3. 3. molecular mechanics and electronic structure <ul><li>In MM, electronic structure changes nuclear geometry </li></ul><ul><li>How do nuclear changes affect electronic structure? </li></ul><ul><li>Conventional answer: they don’t </li></ul><ul><li>Better answer: polarizable charge models </li></ul>http://mfrost.typepad.com/cute_overload/2006/02/peeky_mcpeekers.html
  4. 4. electronegativity  and hardness  <ul><li>Atoms in molecules = thermodynamic systems in contact with external particle bath </li></ul>http://mfrost.typepad.com/cute_overload/2006/02/peeky_mcpeekers.html N, V, T   i E i q i EA IP 2 N i = Z i - q i 0 0
  5. 5. http://www.flickr.com/photos/fantasyfan/35417428 how qtpie works
  6. 6. charge vs. charge transfer variables q 5 q 4 QEq q 3 q 2 q 1 p 12 p 23 p 34 p 45 QTPIE
  7. 7. results <ul><li>dissociating NaCl </li></ul><ul><ul><li>problem in QEq </li></ul></ul><ul><ul><li>finite charge separation when dissociated </li></ul></ul><ul><ul><li>divergent dipole moment </li></ul></ul><ul><li>parameters transferable </li></ul><ul><ul><li>H 2 O for various geometries </li></ul></ul><ul><ul><li>suddenly dissociated NaCl . 6H 2 O </li></ul></ul>
  8. 8. dipole polarizabilities <ul><li>Severely overestimated in QEq </li></ul><ul><li>Less severely so in QTPIE, but still bad ! </li></ul>13.6758 12.3622 6.9981 8.4240 7.0488 0.8595 13.0298 10.7566 0.0000 24.6244 20.3270 0.0000 Phenol 1.5269 1.4566 1.4333 0.8009 0.4208 0.0052 1.8338 0.6516 0.0000 3.4653 1.2317 0.0000 H 2 O 4.7957 4.1384 4.1375 1.2108 0.1391 0.1390 6.2171 0.0000 0.0000 13.9474 0.0000 0.0000 NaCl MP2/3Z MP2/STO-3G QTPIE QEq System
  9. 9. where it’s going <ul><li>rewriting in scientific python </li></ul><ul><li>reparameterization, e.g. using DFTB results </li></ul><ul><li>QTPIE/MM method </li></ul><ul><ul><li>to interface with MDX, a MD library </li></ul></ul><ul><ul><li>study solvated electrons </li></ul></ul>
  10. 10. http://www.flickr.com/photos/fantasyfan/33736090 open questions: treating multiple states
  11. 11. charged systems are really hard <ul><li>Lagrange multipliers v. reparameterization </li></ul><ul><li>e.g.: Na : water : phenol  -stacked system </li></ul>Lagrange multiplier method reparameterize Na: account for formal charge Mulliken/MP2/cc-pVDZ charge: 0.7394 0.8648 0.4798 reparam. 0.1876 0.6177 Lagrange QTPIE QEq q Na /e
  12. 12. still needs brainstorming <ul><li>Charge distributions for excited states </li></ul><ul><li>Theoretical interpretation as coarse-grained quantum mechanical theory? </li></ul><ul><ul><li>Intuitively connected to DFT </li></ul></ul><ul><ul><li>Statistical mechanical interpretation of energy function </li></ul></ul><ul><li>QM definition for charge? </li></ul><ul><ul><li>Proposal: charge needed to define electrostatic force that best approximates the Hellman-Feynman force </li></ul></ul>
  13. 13. miscellany
  14. 14. interlude icqc 2006, kyoto
  15. 15. visualization scripts makemovie visualizes orbital changes along a trajectory
  16. 16. Aromaticity and scattering on a ring <ul><li>Crude model: </li></ul><ul><ul><li>Substituents = ideal metals with well-defined Fermi wavevectors </li></ul></ul><ul><ul><li>Aromatic ring = benzene </li></ul></ul><ul><li>Switching behavior of meta-coupled benzene derivatives </li></ul><ul><ul><li>transmission probability triples from ground to first excited states </li></ul></ul>
  17. 17. http://mfrost.typepad.com/cute_overload/2006/06/perfect_ear_flo.html Any questions?

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