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CM x Charges for SCC-DFTB and Some GaN Vignettes

CM x Charges for SCC-DFTB and Some GaN Vignettes. Christopher J. Cramer University of Minnesota. DFTB Energy Functional. SCC-DFTB Energy Functional. Class II Partial Charges (Population Analysis). L öwdin. Mulliken. Class IV Partial Charges (CM2 and CM3). Mayer bond order. empirical

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CM x Charges for SCC-DFTB and Some GaN Vignettes

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  1. CMx Charges for SCC-DFTB and Some GaN Vignettes Christopher J. Cramer University of Minnesota

  2. DFTB Energy Functional

  3. SCC-DFTB Energy Functional

  4. Class II Partial Charges (Population Analysis) Löwdin Mulliken

  5. Class IV Partial Charges (CM2 and CM3) Mayer bond order empirical linear and quadratic parameters x = 2, Li et al. J. Phys. Chem. A, 1998, 102, 1820. x = 3, Winget et al. J. Phys. Chem. A2002, 106, 10707 Thompson et al. J. Comput. Chem. 2003, 24, 1291

  6. Training Set and Error Functions • Training set roughly 400 neutral and 25 ionic molecules • Compare point-charge derived dipole moments to experimental values • For ions, compare point-charge-derived moments to <||>(MP2/cc-pVTZ, center of mass) and compare partial atomic charges to those determined from CHELPG fit to MP2/cc-pVTZ electrostatic potential

  7. Performance Example

  8. Performance Example 2

  9. Accurate, Density, andCM3Dipole Moments nitramide Cs C2v Cs C2v 3.94 3.59 3.84 4.31 3.93 4.19 2.97 2.712.89 3.28 3.07 3.27 Accurate: mPW0/MG3S density dipole Approximate dipoles MUE  mean unsigned error: MUE (density) = 0.30 debyes MUE (CM3) = 0.08 debyes from mPW0/MIDI!

  10. Accurate, Density, andCM3Dipole Moments dimethylnitramine 4.81 4.21 4.67 5.04 4.43 4.87 3.43 2.99 3.33 3.69 3.38 3.77 MUE  mean unsigned error: MUE (density) = 0.49 debyes MUE (CM3) = 0.12 debyes Accurate: mPW0/MG3S density dipole

  11. Accurate, Density, andCM3Dipole Moments : RDX 5.97 5.22 6.20 7.19 6.22 7.34 MUE  mean unsigned error; MUE (density) = 0.86 debyes MUE (CM3) = 0.19 debyes Accurate: mPW0/MG3S density dipole

  12. Accurate, Density, andCM3Dipole Moments : HNIW; CL-20 [hexa-nitrohexaaza-iso-wurtzitane]    1.56 1.32 1.80 0.31 0.42 0.79 2.56 1.95 2.41 MUE  mean unsigned error: MUE (density) = 0.32 debyes MUE (CM3) = 0.29 debyes Accurate: mPW1PW91/MG3S density dipole

  13. All 14 nitramines (0.2) (2.8) (2.9) MUD (CM3) = 0.1 MUD (ChElPG) = 5.7 MUD (Löwdin) = 5.9 CM3 Delivers Consistent Partial Atomic Charges Polarization energies (in nitromethane) calculated using different charge schemes by wave function (kcal/mole): electrostatic fitting MUD  mean unsigned deviation: population analysis

  14. SCC-DFTB Results — Before Signed errors O(0.4 D), RMSE O(0.7 D)

  15. Optimized Parameters (Mulliken mapping) Linear (in B.O.) parameters quadratic parameters

  16. SCC-DFTB Results — After

  17. CM3 Improvement + Mulliken o CM3

  18. Gallium Nitride from Cyclotrigallazane NH3 [HGaNH]n GaN 150° C substantial cubic form in addition to wurtzite Kormos et al. JACS, 2005, 127, 1493

  19. What is Nature of [HGaNH]n? Kormos et al. JPC A, 2006, 110, 494

  20. What is Nature of [HGaNH]n? Kormos et al. JPC A, 2006, 110, 494

  21. [HGaNH]n Is a Mixture of Nanorods Dipole moment (D) Kormos et al. JACS, 2005, 127, 1493

  22. Error compared to DFT and MP2 • Data set included small molecules containing Ga, N, and H atoms • B3LYP and MP2 with 6-311+G(2df, p) basis set on N and H and CEP-31G ECP and basis set on Ga • Data set included six dimers for binding energies and intermolecular distances, seven reaction energies, and nine molecules for bond lengths and angles

  23. [H2GaNH2]3 Binding Energy and Rod Growth Dimer A

  24. Future Plans • Reparameterize SCC-DFTB to get better agreement with higher levels of theory • Hardness was not found to have sufficient influence • Reoptimize Erep to B3LYP data • Add empirical dispersion term to get better binding energies and distances

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