The Effects of Entropy-calibration Mixing Length Parameter on Structure, Evolution, and Lithium Abundance of Stars

In traditional stellar evolution studies, the mixing-length parameter $\alpha_{\rm{MLT}}$ is usually set as a fixed value. However, many studies have found that $\alpha_{\rm{MLT}}$ should not be constant. The mixing-length parameter $\alpha_{\rm{MLT}}$ can affect the adiabatic entropy of models, and the three-dimensional radiative hydrodynamic simulations can provide the value of adiabatic entropy. Therefore, the simulated adiabatic entropy can be used to calibrate $\alpha_{\rm{MLT}}$. Using two simulated entropy-calibrated models, the variation of $\alpha_{\rm{MLT}}$ with stellar mass and age is investigated. Compared to the standard model, the entropy-calibrated model exhibits a larger radius and lower effective temperature in the early main sequence, whereas the opposite is true in the late main sequence. Consequently, the evolutionary tracks of the entropy-calibrated model differ significantly from those of the standard model. The computational results further reveal that one of the entropy functions is not applicable to the pre-main sequence phase, as it leads to excessive depletion of lithium that is inconsistent with observational data. In contrast, although the other entropy function is more complex, it is applicable to the pre-main sequence phase.