Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Undefined value found in the stiffness matrix.

Please login with a confirmed email address before reporting spam

Hi I am Getting Following error when I am trying to solve Mosfet model in comsol

Undefined value found.
- Detail: Undefined value found in the stiffness matrix.
.There are 9 equations giving NaN/Inf in the matrix rows for the variable mod1.phi0
. at coordinates: (1.85106e-007,-3.45295e-007), (7.68991e-008,-2.18897e-007), (1.31003e-007,-2.82096e-007), (8.2885e-009,-3.71345e-007), (9.66972e-008,-3.5832e-007), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns.

thanks and regards

Pavan Naik

2 Replies Last Post 22.12.2014, 04:31 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 11.11.2012, 04:11 GMT-5
Hi

it mens exactly what is written: some values are mising, ...

the difficulty, I agree, is to identify which values ;)

often it's some material properties, perhaps you have some surface physics and you need a "boundary" material duplicated, or different, from another "domain" material definition; or it's a BC missing.

Have you checked which dependent variables you are solving for ? and do all of them have enough BC values, in absolute (Dirichlet) and or flux (Neumann) and 2 if 2nd order derivatives are involved

--
Good luck
Ivar
Hi it mens exactly what is written: some values are mising, ... the difficulty, I agree, is to identify which values ;) often it's some material properties, perhaps you have some surface physics and you need a "boundary" material duplicated, or different, from another "domain" material definition; or it's a BC missing. Have you checked which dependent variables you are solving for ? and do all of them have enough BC values, in absolute (Dirichlet) and or flux (Neumann) and 2 if 2nd order derivatives are involved -- Good luck Ivar

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 22.12.2014, 04:31 GMT-5
Thank you Ivar, I found my problem in the boundary condition to be incorrect input.
Thank you Ivar, I found my problem in the boundary condition to be incorrect input.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.