**From:** Heyfitch, Vadim (*vadim.heyfitch@intel.com*)

**Date:** Tue Aug 29 2000 - 14:42:38 PDT

**Next message:**ARNOLD,PETER (HP-Cupertino,ex3): "RE: [SI-LIST] : Schematic tools for generating HSPICE file"**Previous message:**Polka, Lesley A: "[SI-LIST] : Q3'00 Intel Technology Journal on-line: packaging issue"**Maybe in reply to:**Jan Vercammen: "[SI-LIST] : question electrostatic solvers"

Jan,

you described the physics perfectly right.

div D = 0 (Maxwell eq.)

Since D=E+4*pi*P, div(E+4*pi*P)=0. But divE=4*pi*rho, where rho is charge

surface density at the dielectric interface. Therefore, div P = - rho.

-Vadim

*> -----Original Message-----
*

*> From: jvercamm@roam.agfa.be [mailto:jvercamm@roam.agfa.be]
*

*> Sent: Tuesday, August 29, 2000 8:12 AM
*

*> To: si-list@silab.eng.sun.com
*

*> Subject: [SI-LIST] : question electrostatic solvers
*

*>
*

*>
*

*> hello si-list,
*

*>
*

*> I have a question concerning method of moments electrostatic solvers.
*

*>
*

*> Some (I think most) general-purpose electrostatic solvers replace the
*

*> dielectric-dielectric interfaces with an unknown surface
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*> charge. So these solvers
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*> atack a free-space problem.
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*>
*

*> My question is: on what is this based? Why is one allowed to
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*> remove the dielectra
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*> and replace them by a surface charge?
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*>
*

*> I do understand (better I think) the following: the
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*> divergence of the polarization P
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*> equals the polarization charge in the dielectric material. A
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*> volume integral of div P
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*> can be reduced to a surface integral over the enclosed volume
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*> (divergence theorem). So
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*> it seems likely that the potential for a location outside the
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*> dielectric volume can
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*> be calculated using the surface charge and a volume
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*> integration is avoided. Is this
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*> correct or am I wrong?
*

*>
*

*> I have checked Paul's book (Analysis of Multiconductor Lines)
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*> and Van Bladel's
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*> (Electromagnetic Fields, page 73+). Paul discusses the matter
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*> briefly but gives no
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*> details. Van Bladel is, as usual, thourough, but I am missing
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*> some points in his
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*> derivation. It will take somewhile to digest this matter.
*

*>
*

*> It would be great if someone could, in plain simple words,
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*> explain the physics behind
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*> this matter or direct me to some detailed exposition or reference(s).
*

*>
*

*> regards,
*

*>
*

*> Jan Vercammen
*

*> Agfa-Gevaert NV
*

*>
*

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*>
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**Next message:**ARNOLD,PETER (HP-Cupertino,ex3): "RE: [SI-LIST] : Schematic tools for generating HSPICE file"**Previous message:**Polka, Lesley A: "[SI-LIST] : Q3'00 Intel Technology Journal on-line: packaging issue"**Maybe in reply to:**Jan Vercammen: "[SI-LIST] : question electrostatic solvers"

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