#parameters that model the material's mechanical properties
    array set $Base {Viscosity {Double 8.0e11}}
    array set $Base {Visc.Exp {Double 0.0}}
    array set $Base {YoungsMod {Double 0.2}}
    array set $Base {PoissRatio {Double 0.0}}
    array set $Base {ViscActVol {Double 0.0}}

    array set $Base {IsNonlinVisc {Boolean {
	[expr [pdbGetDouble Silicon Flow Vol_O] > 0.0]}}}

return { Viscosity Visc.Exp YoungsMod PoissRatio ViscActVol IsNonlinVisc }

