檢視 $negferrortolerance 的原始碼

$negferrortolerance is the command to setup the tolerance for the program to get converged. And the second term is the amplitude of the virtual wave.<br> 
The virtual wave means that there is no electron wave before the system scattering, but the wave function can not be zero in the equation,  so we give a virtual wave to load the scattering wave and complete the calculation. After subtracting the value of the virtual wave, the correct wave function value can be obtained.<br>
Example:
  $negferrortolerance
  1.0e-6 1.0e27