June 2009 Results
Comparison of Velocity Verlet and Predictor Corrector algorithms in microcanonical
ensemble. Comparison of different time steps ( Dt) .
First we tried to monitor the vibrations of carbon nanotube without thermostating
(microcanonical ensemble, KFLAG = 0) with different time step (a) Dt = 0.5 fs; (b) Dt = 1 fs
using Velocity Verlet integrator and the same test with Predictor Corrector integrator. The
results showed that the results, which use code with the Velocity Verlet are not affected by the
change of the time step, however the code, which uses Predictor Corrector integrator gives
different results for Dt = 0.5 fs and Dt = 1 fs. We decided to change the time step for the
Predictor Corrector integrator to 0.25 fs and 2.0 fs.
The results are presented in Table 1 and Table 2.
Table 1. Microcanonical ensemble without previous thermalization. Velocity
mode Dt = 0.5 fs Dt = 1.0 fs
f (THz) Power (2
) f (THz) Power(2
1 0.2808 3.839*10-4