Are van der Waals coefficients independent of temperature? In the van der Waals equation for real gases, the coefficients $a$ and $b$ are used as respective correction terms for pressure and volume in the ideal gas equation.

I want to know whether the van der Waals coefficients are independent of absolute temperature or not.
The van der waals constant can be directly obtained from the critical temperature and pressure. We have,

${a = \frac{27 R^2 T_c^2}  {64 P_c}}$
${b =  \frac{R T_c }{ 8 P_c}}$

Since, $T_c$ and $P_c$ are constants, we can conclude that the van der waals constants are really &quot;constants.&quot;