Am stimulating sequential coupled thermomechanical analysis in abaqus standard but abaqus terminate the job when the second step is started warring system matrix have 300? Negative eigenvalues
If you have negative eigenvalues that means that your system of equation is not positive definite. The physical meaning is, that you won't fullfill Newton's law
sum F != 0
because your reaction force shows in the same direction as your applying force.
The reason in a multidimensional analysis is typically, that you chose the wrong parameter set. If some coupling parameter of yours are to large (or have the wrong sign) it might lead to negative eigenvalues. Try to reduce them.