Theoretical and Computational Chemical Sciences
at UT-Austin
~molecular focus.James R. ChelikowskyRon Elber· biomolecular dynamics; bioinformaticsGraeme Henkelman· condensed matter dynamics.Dmitrii E. Makarov· biopolymers, single molecule phenomena.Peter J. Rossky· dynamics in solution + amorphous materials.John F. Stanton· excited state structure, reactivity.Robert E. Wyatt· quantum dynamics of molecular systems.
~materials focusRoger T. Bonnecaze· interfacial phenomena, fluid dynamics.James R. Chelikowsky· computational materials science.Venkat Ganesan· advanced polymeric materials.Gyeong S. Hwang· dynamics of solid state materials.Peter J. RosskyIsaac C. Sanchez· statistical thermodynamics of polymers.Thomas M. Truskett· energy landscapes -complex systems.
Faculty in Theoretical Chemistry
Chemistry Chemical Engineering
Rossky group researchRossky group researchDepartment of Chemical Engineering
Center for Computational Molecular Science (ICES)and Department of Chemistry and Biochemistry
MolecularMolecular mechanisms for chemical behavior - liquids / solutions / amorphous materials
Methods - Theory and simulationclassical and quantum statistical mechanics
at an atomistic and electronic level
Recent/current projects
solvent influences - biopolymer hydration protein interactions/stability- supercritical fluids: surfactants for novel solvents
condensed phase electronic and nuclear quantum dynamics- development of feasible algorithms for large systems- photochemistry; molecular electronic materials- spectroscopy, esp. ultrafast transient spectroscopy
Classical, atomistic, molecular dynamics simulation
‘Solvation’-
Hydration of biopolymer interfaces -role of chemical character and topology
Stability at low temperature –onset of cold unfolding; relation to cryopreservation?
Supercritical solvents (w/ Keith Johnston, ChE)
CO2 – solubility and interfaces -conceptual basis for surfactant design:
H2O microemulsionsnanoparticle synthesis and dispersion
rational ligand design
Simulation details:A neutron diffraction structure for sperm whale myoglobin was used as the starting point for simulations (PDB ID: 1CQ2). The HEME was removed, and the structure was fully solvated (SPC/E water). Simulation was run using NAMD program in the NPT ensemble at 510K and 1atm for 2ns.
2. Eliezer, D., Wright, P. E.“Is Apomyoglobin a Molten Globule? Structural Characterization by NMR”.
263, 531-538J. Mol.
Biol. 1996,
Apomyoglobin -Cold denaturation
Snapshots of SC changeSnapshot of VAL 114 at 310K (left) and 278K (right) near the end of the simulations runs. At 310K the residue is buried inside a hydrophobic pocket, but at 278K it is exposed to and surrounded by solvent.
Snapshot of ARG 45 at 310K (left) and 278K (right) near the end of the simulation runs. At 310K the pocket next to the residue is quite narrow and water cannot penetrate within. At 278K however, the interstitial space increases and water is in contact with the non-polar atoms within the pocket.
310K 278K
harmonic
ΔΔRMS atomic fluctuations onRMS atomic fluctuations on coolingcooling
Local isothermal compressibilityLocal isothermal compressibilityvolume fluctuations for atom groups based on space tesselation,
(following C. B. Post)
310K
278K
largest “anomalies”lie in the core.
enhanced position fluctuations
enhanced compressibility
UPON COOLING
Fig. 5“FRONT” “SIDE”
“hot spots” are in the CORE, not surface
CorrelationsCorrelations
enhanced atomic position fluctuations
regions of enhanced compressibility(“free volume”)
g (r)
Electronic / nuclear dynamics, and spectroscopy(methods + applications of quantum-classical/semiclassical simulation)
photochemistryexcited state dynamics and relaxationelectron transfer
electronic excitations and structure
organic electronic materials –energy trapping and transportphotoexcited statescharge carrier dynamics
clusters as models of bulk solvents –solvated electrons in water clusters
hν
π-electrons + molecular mechanics
Abs
PL
DIMERS – 2 x 5-mer @ 300K (in vacuo) 90 carbon atom system
Ground state optical absorption spectrum -“H-aggregate”-like: S2 is bright state
Excited state energy gaps (S2-S1): strongly modulated by structural fluctuations -
benzoid-quinoid shift ←→ Δ[charge]
Exciton (S1) localization and hopping in 2 x (5)OPV- contour plot of DR2
Delayed polaron pair formation in 2 x (7)OPV~ 3.1 eV initial excitation into S2 delayed formation ~ 20% cases ultrafast formation (< ~50 fs) ~ 15% cases
This example: delayed NA transition
to S1 via S3 at t ~ 500 fs
NA transition of an S2 EX to S1 PP never seen.
Delayed polaron pair formation in 2 x (7)OPV~ 3.1 eV initial excitation into S2 delayed formation ~ 20% cases ultrafast formation (< ~50 fs) ~ 15% cases
This example: delayed NA transition
to S1 via S3 at t ~ 500 fs
NA transition of an S2 EX to S1 PP never seen.
THANKS FOR YOUR ATTENTION!
THANKS FOR YOUR ATTENTION!
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