  This study investigates the ultraslow diffusion by a spatial structural
derivative, in which the exponential function exp(x)is selected as the
structural function to construct the local structural derivative diffusion
equation model. The analytical solution of the diffusion equation is a form of
Biexponential distribution. Its corresponding mean squared displacement is
numerically calculated, and increases more slowly than the logarithmic function
of time. The local structural derivative diffusion equation with the structural
function exp(x)in space is an alternative physical and mathematical modeling
model to characterize a kind of ultraslow diffusion.
