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2.3QuantumChemistry
ThedensitydifferencesΔρ arenowapproximatedasatomic contributions:
Δρ=∑
α Δρα (2.24)
Now, thechargemonopoleapproximation isused for theatomicdensity functions.
Δρα≈ΔqαFα00Y00 (2.25)
Here,Fα00 is thenormalizedradialdependenceof thedensityfluctuationonatomα
which is approximated tobe spherical (Y00).
The resultingapproximated secondorder energy termshas two limiting cases:
1. When atoms α and β are at a largedistance (>2Å), the exchange correlation
energy becomes zero. In this case, the integral only describes the Coulomb
interactionof twopoint charges.
E2nd≈ 1
2∑
αβ ΔqαΔqβ
Rαβ (2.26)
2. For α = β, the integral describes the electron-electron interaction on a single
atomα
E2nd= 1
2 UαΔq2α (2.27)
TheparameterUα is theHubbardparameter newly introduced inDFTB2 andde-
scribes the chemical hardness of the atomα. It is ameasure for the energy change
of a systemuponadditionor removal of electrons.
In conclusion, this introducedmethod is an approximativeDFTmethodwhich is
up to 3orders ofmagnitude faster thanDFT. This is achievedbyusing aminimal
basis set for thevalence electronsof everyatomaswell aspre-calculatingand tab-
ulating two-center integrals forall atompairs. Therefore,DFTB2 is able todescribe
large systems likeDNAoverextendedperiodsof timeand is themethodof choice
for the charge transfer calculation in thiswork.
23
Charge Transport in DNA
Insights from Simulations
- Titel
- Charge Transport in DNA
- Untertitel
- Insights from Simulations
- Autor
- Mario Wolter
- Verlag
- KIT Scientific Publishing
- Datum
- 2013
- Sprache
- englisch
- Lizenz
- CC BY-SA 3.0
- ISBN
- 978-3-7315-0082-7
- Abmessungen
- 17.0 x 24.0 cm
- Seiten
- 156
- Schlagwörter
- Charge Transport, Charge Transfer, DNA, Molecular Dynamics, Quantum Mechanics
- Kategorien
- Naturwissenschaften Chemie
Inhaltsverzeichnis
- Zusammenfassung 1
- Summary 3
- 1 Introduction 5
- 2 TheoreticalBackground 11
- 3 SimulationSetup 39
- 4 DNAUnderExperimentalConditions 49
- 5 ChargeTransport inStretchedDNA 69
- 6 ChargeTransport inMicrohydratedDNA 79
- 7 AParametrizedModel toSimulateCT inDNA 89
- 8 Conclusion 105
- Appendix 111
- A DNAUnderExperimentalConditions 111
- B CTinMicrohydratedDNA 117
- List ofPublications 137