this talk has only three equations Jiahao Chen Vieques, PR http://mfrost.typepad.com/cute_overload/2006/05/bullbl
Jan 27, 2015
this talk has only three equationsJiahao ChenVieques, PR
http://mfrost.typepad.com/cute_overload/2006/05/bullblob.html
qtpie: how cute can you get?
http://mfrost.typepad.com/cute_overload/2006/02/peeky_mcpeekers.html
http://mfrost.typepad.com/cute_overload/2006/02/peeky_mcpeekers.html
molecular mechanics and electronic structure
• In MM, electronic structure changes nuclear geometry
• How do nuclear changes affect electronic structure?
• Conventional answer: they don’t• Better answer: polarizable charge
models
http://mfrost.typepad.com/cute_overload/2006/02/peeky_mcpeekers.html
electronegativity and hardness
• Atoms in molecules = thermodynamic systems in contact with external particle bath
N, V, T
i
Ei qi
EA
IP2
Ni = Zi - qi
00
http://www.flickr.com/photos/fantasyfan/35417428
how qtpie works
charge vs. charge transfer variables
q5q4
QEq
q3
q2
q1 p12
p23
p34
p45
QTPIE
results
• dissociating NaCl– problem in QEq– finite charge separation
when dissociated– divergent dipole
moment
• parameters transferable– H2O for various
geometries– suddenly dissociated
NaCl.6H2O
dipole polarizabilities• Severely overestimated in QEq• Less severely so in QTPIE, but still bad!
System QEq QTPIEMP2/STO-
3GMP2/3Z
NaCl13.9474
0.00000.0000
6.21710.00000.0000
1.21080.13910.1390
4.79574.13844.1375
H2O3.46531.23170.0000
1.83380.65160.0000
0.80090.42080.0052
1.52691.45661.4333
Phenol24.624420.3270
0.0000
13.029810.7566
0.0000
8.42407.04880.8595
13.675812.3622
6.9981
where it’s going
• rewriting in scientific python• reparameterization, e.g. using DFTB
results• QTPIE/MM method
– to interface with MDX, a MD library– study solvated electrons
http://www.flickr.com/photos/fantasyfan/33736090
open questions: treating multiple states
charged systems are really hard
• Lagrange multipliers v. reparameterization
• e.g.: Na : water : phenol -stacked system
qNa/e QEq QTPIE
Lagrange
0.6177 0.1876
reparam.
0.4798 0.8648
Lagrange multiplier method
reparameterize Na: account for formal charge
C2 C1
C3
C4C5
C6 O7
H11
Na17
H14
H15 H16
H13 H12
O8
H9 H10
Mulliken/MP2/cc-pVDZ charge: 0.7394
still needs brainstorming
• Charge distributions for excited states• Theoretical interpretation as coarse-
grained quantum mechanical theory?– Intuitively connected to DFT– Statistical mechanical interpretation of
energy function
• QM definition for charge?– Proposal: charge needed to define
electrostatic force that best approximates the Hellman-Feynman force
interlude
icqc 2006, kyoto
makemovie visualizes orbital changes along a trajectory
visualization scripts
Aromaticity and scattering on a ring
• Crude model:– Substituents = ideal
metals with well-defined Fermi wavevectors
– Aromatic ring = benzene
• Switching behavior of meta-coupled benzene derivatives– transmission probability
triples from ground to first excited states
R1
R2
http://mfrost.typepad.com/cute_overload/2006/06/perfect_ear_flo.html
Any questions?