Urgent!! Help about NDSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg28685] Urgent!! Help about NDSolve*From*: "Diego Martin Martin" <diego at ies-def.upm.es>*Date*: Wed, 9 May 2001 04:20:06 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hello, I work on semiconductor manufacturing. Now Im trying to simulate the behaviour of a p-n juntion (with some particular changes) in a semiconductor with Mathematica 4.0. I have a problem when I try to solve the Continuity Equation for minoritary electrons in the p-type region. This is a Linear with Non-Constant Coefficients Ordinary Differential Equation with boundary conditions involving both the function and its derivatives at the start and end of the integration interval. When I try to solve it usind NDSolve, I obtain a numerical solution that is not correct. Is there some other function or package to solve non-linear differential equations? Could I obtain some improvement doing the traslation to a system of diff. equations? Sometimes I obtain an error message that sais I must increase the WorkingPrecision option, because when trying to evaluate some expresion the limit was reached. I have tryed to change the AccuracyGoal, PrecisionGoal and WorkingPrecision options, but the numerical solution remain incorrect. What can I do to solve this problem? Thank you in advance. Regards, Diego.