Excited state calculations for polyene and PPV systems
description
Transcript of Excited state calculations for polyene and PPV systems
Excited state calculations for polyene and PPV systems
Chao Wu
Contents
• Introduction
• Computational method
• Results and Discussion
• Difficulty met
• Future work
Introduction• Conjugated molecules have potential a
pplications in optoelectronic devices, photo dynamic therapy and biological imaging, etc. because of their optical properties
• Polarizability, conformational change, electronic density variations, etc. can not be studied by experimental methods only as they all involve coupled electron-nuclear structure dynamics.
• The connection between electronic structure and the optical properties of these compounds forms a complex and fundamental problem.
Introduction
• These optical properties involve time dependent photochemical process with non-adiabatic excitation/relaxation
• Ground state adiabatic calculation is not enough
• Aiming at excited states energy calculation, this project provides a basis training for the future work in this area
Introduction
• The systems for calculation are polyacetylene(n=2~6) and poly phenylene vinylene (PPV, n=2~5) oligomers which are both promising photonics materials under intensive investigation.
Computational method
egge ˆ2
2
3
2
e
mf
ge
ge
Age 2
Computational method
• Gaussian03(both on local PC & Grid)
• For polyacetylenes:• HF/3-21G CIS/3-21G and TDHF/3-21G• B3LYP/3-21GTDB3LYP/3-21G• B3LYP/6-31+GTDB3LYP/6-31+G• AM1ZINDO
• For PPV:• HF/3-21G CIS/3-21G• AM1ZINDO
Results and Discussion
• For polyacetylene system,• The optimized structures (ground state)
are trans-planar. (C2h symmetry).
• The excitation energy calculation, we used singlet spin and 10 states for investigation.
• We got transition dipole moment, oscillator strengths, and vertical excitation energies.
Molecule level Osc. Stren. Transition energy (eV)
Butadiene
CIS/3-21G 1.2214 7.2413
TDHF/3-21G 0.9189 6.8280
TDB3LYP/3-21G 0.6669 6.2564
TDB3LYP/6-31+G 0.6701 5.6542
ZINDO 0.9081 5.4016
Hexatriene CIS/3-21G 1.7949 6.1503
TDHF/3-21G 1.4032 5.8137
TDB3LYP/3-21G 1.0600 5.0336
TDB3LYP/6-31+G 1.0970 4.6648
ZINDO 1.2886 4.4703
Octatetraene CIS/3-21G 2.3481 5.4623
TDHF/3-21G 1.9052 5.1763
TDB3LYP/3-21G 1.4707 4.2716
TDB3LYP/6-31+G 1.5211 4.0038
ZINDO 1.6603 3.9226
Decapentaene CIS/3-21G 2.8727 4.9980
TDHF/3-21G 2.4141 4.7469
TDB3LYP/3-21G 1.8832 3.7427
TDB3LYP/6-31+G 1.9407 3.5311
ZINDO 2.0166 3.5643
Dodecahexene CIS/3-21G 3.3725 4.6683
TDHF/3-21G 2.9244 4.4411
TDB3LYP/3-21G 2.2910 3.3523
TDB3LYP/6-31+G 2.3543 3.1746
ZINDO 2.3579 3.3144
Polyacetylene
S. M. Smith et al., J. Phys. Chem. A 2004, 108, 11063-11072.
Dodecahexene HOMO
Dodecahexene LUMO
PPV
• For PPV system, the optimized structures are not planar: librational motion also pertubation (impurity and intermolecular interaction)
• Verified by experimental results
PPV5 non-planar ground state geometry optimized at AM1
Molecule Level Osc. Stren. Transition Energy(eV)
PPV2 CIS/3-21G 1.1900 5.1883
ZINDO 0.8975 4.0902
PPV3 CIS/3-21G 1.8463 4.6044
ZINDO 1.7585 3.4727
PPV4 CIS/3-21G * *
ZINDO 2.4457 3.2885
PPV5 CIS/3-21G * *
ZINDO 2.8725 3.5141
* Result not got yet
PPV
S. Tretiak, A. Saxena, R. L. Martin, A. R. Bishop, Phys. Rev. Lett., 89, 9, 097402-1~4.
Difficulty
• Limited experience on calculation
• Limited calculation resource on local computer
• For excited state calculation, the RWF is too big and sometimes hard to predict
Future work• Finish planned calculation• Optimize PPV excited state geography• Compare PPV excited state bond length• Calculate PPV excited state reorganizatio
n energy and fluorescence frequency (can calculate stoke shift)
• Calculate polarizability and other optical properties
Acknowledgement
• Dr. Smriti Anand
• Dr. Schlegel
• Dr. Chernyak
• Ph.D. students:
Stanley M. Smith
Jie Li
Thank you
Q & A