Apparently easy ODE

*To*: mathgroup at smc.vnet.net*Subject*: [mg22922] Apparently easy ODE*From*: Kurt Taretto <Kurt.Taretto at ipe.uni-stuttgart.de>*Date*: Thu, 6 Apr 2000 02:04:38 -0400 (EDT)*Organization*: Comp.Center (RUS), U of Stuttgart, FRG*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I'm having some problems solving PDE's, for example the folowing notebook Clear["Global`*"]; (* constants definitions *) Es =11.8*8.85418`50*10^-14; q = 1.60218`50*10^-19; Nd = 1.0`50*^16; g = 1.0`50*^-4; G = 1.0`50*^20; u= 500.0`50; DD = 25.0`50; k1 = q/Es; solution = NDSolve[{e'[x] == k1 p[x], G - u e'[x] p[x] - u e[x] p'[x] + DD p''[x] == 0, e'[0] == 0, p[g] == 1.0`50*^10, p'[0] == 0}, {e, p}, {x, 0, g}, WorkingPrecision -> 20]; Plot[p[x] /. solution, {x, g/100, g}, PlotRange -> All]; causes an error message, "Cannot find starting value for the variable x.", and obviously no solution is given. Apparently this error message is about the internals of the algorithm, but I can't figure out what I'm doing wrong. Any help on this would be appreciated. Thanks! Kurt Taretto