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Hi!

We recently installed COMSOL 4.2. (We've been using COMSOL 3.5a, so we are trying to create the same model on COMSOL 4.2. The model works with COMSOL 3.5a version)

Basically, I am working on "Transport of Diluted Species" module, where I want periodic condition from left and right of my slab of brick and mortar geometry.

I set my bricks to be impermeable by putting zero diffusivity, and I put a value for mortar geometry. And I set top mortar to have a certain concentration (infinite source), and I set the bottom mortar to have zero concentration (infinite sink). My brick and mortar is a 2D geometry, and I put periodic condition on left and right side of my rectangular slab. I basically want my solutes to go through mortar pathway, but for some reasons, it's not working on this model.

I guess I am doing something wrong, I got below error message from COMSOL 4.2

Undefined value found.
- Detail: Undefined value found in the stiffness matrix.
There are 253 equations giving NaN/Inf in the matrix rows for the variable mod1.c
at coordinates: (4.01e-005,1.75e-005), (4.01e-005,1.74437e-005), (4.01e-005,1.73683e-005), (4.01e-005,1.72675e-005), (4.01e-005,1.71327e-005), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns

What am I doing wrong?