Section SHELL_OPT

• This section sets the environment for the optimization of the shell-core distances that might turn to be necessary along a MD run using a shell-model potential. The optimization procedure is activated when at least one of the shell-core pairs becomes too elongated, i.e. when the assumption of point dipole is not longer valid.

• Section path: CP2K_INPUT / MOTION / SHELL_OPT

• This section cannot be repeated and can be optional.

• Subsections

  • BFGS
  • CG
  • LBFGS
  • PRINT

• Keywords

  • MAX_DR
  • MAX_FORCE
  • MAX_ITER
  • OPTIMIZER
  • RMS_DR
  • RMS_FORCE
  • STEP_START_VAL

• Keyword descriptions

  MAX_DR
  	MAX_DR {REAL}
  	Convergence criterium for the maximum geometry change between the current and the last optimizer iteration.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.00000000E-03
  	Default unit: [bohr]

  MAX_FORCE
  	MAX_FORCE {REAL}
  	Convergence criterium for the maximum force component of the current configuration.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 4.50000000E-04
  	Default unit: [bohr^-1hartree]

  MAX_ITER
  	MAX_ITER {INTEGER}
  	Specifies the maximum number of geometry optimization steps. One step might imply several force evaluations for the CG and LBFGS optimizers.
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 200

  OPTIMIZER
  	OPTIMIZER {BFGS|LBFGS|CG}
  	Specify which method to use to perform a geometry optimization.
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: BFGS
  	List of valid keywords: BFGS Most efficient minimizer, but only for 'small' systems, as it relies on diagonalization of a full Hessian matrix CG conjugate gradients, robust minimizer (depending on the line search) also OK for large systems LBFGS Limit memory variant of the above, can also be applied to large systems, not as well fine-tuned
  	Alias names for this keyword: MINIMIZER
  	This keyword cites the following reference: [BYRD1995]

  RMS_DR
  	RMS_DR {REAL}
  	Convergence criterium for the root mean square (RMS) geometry change between the current and the last optimizer iteration.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.50000000E-03
  	Default unit: [bohr]

  RMS_FORCE
  	RMS_FORCE {REAL}
  	Convergence criterium for the root mean square (RMS) force of the current configuration.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.00000000E-04
  	Default unit: [bohr^-1hartree]

  STEP_START_VAL
  	STEP_START_VAL <INTEGER>
  	The starting step value for the SHELL_OPT module.
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0