  Convective-core overshoot mixing is a significant uncertainty in stellar
evolution. Because numerical simulations and turbulent convection models
predict exponentially decreasing radial rms turbulent velocity, a popular
treatment of the overshoot mixing is to apply a diffusion process with
exponentially decreasing diffusion coefficient. It is important to investigate
the parameters of the diffusion coefficient because they determine the
efficiency of the mixing in the overshoot region. In this paper, we have
investigated the effects of the core overshoot mixing on the properties of the
core in solar models and have constrained the parameters of the overshoot model
by using helioseismic inferences and the observation of the solar 8B neutrino
flux. For solar-mass stars, the core overshoot mixing helps to prolong the
lifetime of the convective core developed at the ZAMS. If the strength of the
mixing is sufficiently high, the convective core in a solar model could survive
till the present solar age, leading to large deviations of the sound-speed and
density profiles comparing with the helioseismic inferences. The 8B neutrino
flux also favours a radiative solar core. Those provide a constraint on the
parameters of the exponential diffusion model of the convective overshoot
mixing. A limited asteroseismic investigation of 13 Kepler low-mass stars with
1.0 < M < 1.5 shows a mass-dependent range of the overshoot parameter. The
overshoot mixing processes for different elements are analyzed in detail. It is
found that the exponential diffusion overshoot model leads to different
effective overshoot mixing lengths for elements with different nuclear
equilibrium timescale.
