//- how explicit component of sigma is to be calculated
word divDSigmaExpMethod
(
    mesh.solutionDict().subDict("solidMechanics").lookup("divSigmaExp")
);

Info << "divSigmaExp method " << divDSigmaExpMethod <<  endl;
if
(
    divDSigmaExpMethod != "standard"
 && divDSigmaExpMethod != "surface"
 && divDSigmaExpMethod != "decompose"
 && divDSigmaExpMethod != "laplacian"
)
{
    FatalErrorIn(args.executable())
        << "divSigmaExp method " << divDSigmaExpMethod << " not found!" << nl
        << "valid methods are:\nstandard\nsurface\ndecompose\nlaplacian"
        << exit(FatalError);
}