1. GEANT4-DNA New physics models …from cell to DNA Christophe Champion
FKPPL Workshop
Seoul March 8-10, 2011

2. The classical Trajectory Monte Carlo - Classical Over Barrier model
From water to DNA:
The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
Input dynamical data :
Each simulation starts and stops at large internuclear distance (≈100 a.u.)
the projectile velocity (VP)
the impact parameter (b)
the initial conditions for the target

3. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
The molecular binding energies

4. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
General features of the classical models
Movements of the particles described by Newton laws
Initial targets information = the knowledge of the binding energies
Classical criteria for describing the ionizing processes
Total cross sections:

5. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
COB (Classical Over Barrier) criteria

6. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
COB (Classical Over Barrier) criteria

7. The Classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
COB (Classical Over Barrier) criteria
Potential seen by the bound electron e1:
where
and
where at the beginning of the simulation

8. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
Propagation of the system
At each step Δt (≈10-2 a.u.) COB and d conditions are tested:
At each time step t and for each involved particle i (i = P, T and/or e-)
For the next time step : t’ = t + Δt

9. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
Conditions and criteria of the final state
kinetic energy of the electron relatively to the target or the projectile
potential energy of the electron relatively to the target or the projectile

10. The classical Trajectory Monte Carlo - Classical Over Barrier model
(CTMC-COB)
Total cross sections for the main ionizing processes induced by charged particles
Abbas et al., Phys. Med. Biol. 53, N1-N11 (2008)
Lekadir et al., NIM B 267, (2009)
Lekadir et al., Phys. Rev. A 79, (2009)

11. From water to DNA: Quantum mechanical approaches:
Coulomb Born approximation (CB1)
Continuum Distorted Wave – Eikonal Initial State (CDW-EIS)
Champion et al., Phys. Med. Biol. 55, (2010)
Target description
LCAO: Linear Combination of Atomic Orbitals
Bernahrdt and Paretzke (Int. J. Mass Spectrom. 599 (2003))

12. Quantum mechanical /classical approaches: CB1, CDW-EIS / CTMC-COB
Ionization of DNA bases impacted by light ions
Abbas et al., Phys. Med. Biol. 53, N1-N11 (2008)
Lekadir et al., NIM B 267, (2009)
Lekadir et al., Phys. Rev. A 79, (2009)
Protons a-particles Carbon ions C6+

13. Quantum mechanical approaches:
Continuum Distorted Wave – Eikonal Initial State (CDW-EIS)
Capture on DNA bases impacted by light ions
Protons Carbon ions C6+

14. DNA versus liquid water:
GEANT4 simulations
Results
DNA 10 bp target
Nucleosome target
An increase of the mean energy value of energy deposits of the order of
25% for the 10 base pairs target and 25% for the nucleosome target