Page - 99 - in Charge Transport in DNA - Insights from Simulations

7.4ChargeTransferExtensions thepolarization inducedbythechargeonanucleobasealso influences the IPof the neighboring nucleobases. With increasing distance, this influence is decreasing. Table7.4 shows theobtainedmeanvaluesof IP for thechargednucleobaseand the fiveneighboringnucleobases. Table7.4: Lowering of IP due to environment polarization. Charge (hole) is localized on nucleobase 0; 1-5 indicating neighboring nucleobases in increasing dis- tance. See alsofigure7.6 nucleobase 0 1 2 3 4 5 Δ IP [eV] −3.373 −2.326 −1.344 −0.828 −0.463 −0.159 Figure7.6: Graphical illustrationof thedecreasedIPinachargedsystem. Thecharge is fully localizedonthenucleobase in themiddle (0, showninred). Neighbor- ingnucleobases (1and2, shown inblue) are influencedby thepolarization induced by the charge on the nucleobase in the middle, albeit to a lesser extend Now, to implement this effect, a shift of themodeled IPwas introduced. In afirst step, theIParecreatedaccordingtotheproceduresshownabove.Afterwards, these IP are loweredby the calculated energy shiftsweightedby the chargepopulations oneachnucleobase. RelaxationTime Withthesetupdescribedsofar, theenvironmentre-polarizes instantaneouslywhen- ever aCTevent has takenplace. This behaviorwouldneglect the fact that it takes a certain period of time for the environment to accommodate for the new charge distribution. Therefore, IP should not adjust instantaneously. To overcome this issue, a relaxationuponaCTeventhas tobe implemented. 99