Time step length

The model runs were carried out for a simulation time of 250 years with a time step length of 10 days. 

The kinetic parameters for DOC biodegradation and solid carbonate precipita-tion/dissolution are given in Table 11.5. For calcite precipitation and dissolution rate constant were assigned for both solid carbonates. The simulation time was 100 years with a time step length of 10 d. 

Note that the presence of two B characters in the string results in halving the corresponding piece s time step length. As we need the method to be consistent, we require that the each of the A, B and O pieces are propagated in time for a total time of h. As a result we use the convention that if a letter appears k times in a method s string, then each individual update piece uses a timestep h/k. For example, the scheme denoted [OABOAOBAO] has an update... 

One obvious remedy for this problem is to choose time-step lengths so as to avoid small integer multiples of half-periods of any oscillatory motion. However, it has been demonstrated that the molecular dynamics potential gives rise to motion with a continuum of periods greater than or equal to 10 fs. Furthermore, the energy instability of impulse MTS methods becomes exponentially worse at larger multiples of the half-periods. This rules out the possibility that a fortuitously chosen assortment of impulse multiple time steps longer than 5 fs could yield stable trajectories. 

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