The minimize keyword

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Purpose

  • This keyword is used to minimize the energy of the system. Currently, only the steepest descent method has been implemented.

Grammar

  • This keyword is used as follows:
   minimize sd force_tolerance maximal_number_of_steps
  • sd means using the steepest descent method.
  • force_tolerance is in units of eV/A. When the largest absolute force component among the [math]3N[/math] force components in the system is smaller than force_tolerance, the energy minimization process will stop even though the number of steps (interations) performed is smaller than maximal_number_of_steps
  • maximal_number_of_steps is the maximal number of steps (interations) to be performed for the energy minimization process.

Examples

Example 1

  • For example, the command
   minimize sd 1.0e-6 10000

means that one wants to do an energy minimization using the steepest descent method, with a force tolerance of 1.0e-6 eV/A for maximally 10000 steps.

Example 2

  • If you have no idea how small force_tolerance should be, you can simply asign a negative number to it:
   minimize sd -1 10000

In this case, the energy minimization process will definitely run 10000 steps.

Caveats

  • This keyword should occur after all the potential keywords.
  • Currently, the simulation box is fixed during the energy minimization.