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One problem with the Newton method arises from the fact, that the Jacobian
matrix cannot be calculated exactly. Especially as the model parameters
depend on many other quantities consideration of all derivatives would be very
complicated. These missing derivatives can cause divergence of the Newton
method at the beginning of the iteration. As reported in [36]
it is advantageous to ignore some of the derivatives of the system matrix at
the beginning of the iteration process. This reduces the coupling of the
equations and is especially useful in case of HD simulations where the
derivatives of the carrier concentrations with respect to the carrier
temperatures deteriorate the convergence properties. As default we ignore
*n*/*T*_{n} and
*p*/*T*_{p} when
*E*_{2}(**u**) > *E*_{th} = 1.0^{ . }*V*_{T}. This is specified by

HDBlock
{
ignoreDer = if (updateNorm > ignoreDerNorm, "EleDEtm,HolDHtm", "");
}

*Tibor Grasser *

1999-05-31