Section MIXED_CDFT

• Calculate properties involving multiple constrained states. The system can be propagated using only two of the CDFT states selected by the keyword FORCE_STATES. The forces are then determined by a linear combination between these two force_eval: F= lambda F1 + (1-lambda) F2. When the keyword MIXED&NGROUPS is set to 2, the CDFT states are solved in parallel (supports only two states with identical constraint definitions), whereas when it is set to 1, the states are solved in serial (supports any number of states and nonequal constraint definitions but the number of constraints must be the same across states).

• Section path: CP2K_INPUT / FORCE_EVAL / MIXED / MIXED_CDFT

• This section cannot be repeated.

• This section cites the following reference: [Holmberg2017]

• Subsections

  • PRINT

• Keywords

  • CI
  • COUPLING
  • DLB
  • EPS_OCCUPIED
  • EPS_SVD
  • FORCE_STATES
  • LAMBDA
  • LOAD_SCALE
  • LOWDIN
  • METRIC
  • MORE_WORK
  • NONORTHOGONAL_COUPLING
  • SCALE_WITH_OCCUPATION_NUMBERS
  • VERY_OVERLOADED
  • WFN_OVERLAP
  • WFN_RESTART_FILE_NAME

• Keyword descriptions

  CI
  	CI {Logical}
  	Perform a CDFT configuration interaction calculation (CDFT-CI). The CI vector is expanded in the basis of the CDFT states. Diagonalizes the nonorthogonal diabatic CDFT Hamiltonian. The energies and expansion coefficients of the CDFT-CI states are outputted. Keyword COUPLING must be active to use this feature.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.
  	Alias names for this keyword: CONFIGURATION_INTERACTION

  COUPLING
  	COUPLING {Integer}
  	Parameter determining how often the CDFT electronic coupling element is calculated. Use a negative number to disable and 0 means every step. By default, the coupling is calculated by rotating the CDFT states to eigenstates of the weight function matrix when a single constraint is active and the constraint definitions are identical in both CDFT states. Otherwise uses Lowdin orthogonalization. For more than two CDFT states, the couplings are not computed pairwise and the values might deviate from values computed separately for each unique CDFT state pair.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: -1

  DLB
  	DLB {Logical}
  	Controls the activation of dynamic load balancing during a mixed CDFT calculation. Requires Gaussian cavity confinement. Works only when the CDFT states are treated in parallel.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  EPS_OCCUPIED
  	EPS_OCCUPIED {Real}
  	Threshold for determining which molecular orbitals are considered occupied when fractional and/or empty orbitals are employed. Can and usually should be less than the threshold EPS_FERMI_DIRAC defined in section SCF&SMEAR. Note that the number occupied MOs should be constant in each CDFT state, since the CDFT coupling is only defined between states in the same spin state. Fractionally occupied MOs might exhibit linear dependencies and a singular value decomposition (EPS_SVD) can be used for removing these.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-006

  EPS_SVD
  	EPS_SVD {Real}
  	Determines the matrix inversion solver needed to compute the coupling. Default value implies LU decomposition, while values between 0.0 and 1.0 imply SVD decomposition. For SVD, the value acts as a threshold for screening singular values so that only values above it are included in the matrix pseudoinverse.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+000

  FORCE_STATES
  	FORCE_STATES {Integer} {Integer}
  	Defines the CDFT states used to propagate the system.
  	This keyword cannot be repeated and it expects precisely 2 integers.
  	Default values: 1 2

  LAMBDA
  	LAMBDA {Real}
  	Specify the mixing parameter lambda in the formula.
  	This keyword cannot be repeated and it expects precisely one real.

  LOAD_SCALE
  	LOAD_SCALE {Real}
  	Control parameter for dynamic load balancing during a mixed CDFT calculation. See code for details.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 2.00000000E+000

  LOWDIN
  	LOWDIN {Logical}
  	Compute the CDFT electronic coupling element using Lowdin orthogonalization. This is the default behavior with multiple constraints and nonidentical constraints. By activating this keyword, this method is also used to compute the the coupling when a single constraint is active in addition to the standard method.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  METRIC
  	METRIC {Logical}
  	Compute reliability metric for the CDFT electronic coupling element by diagonalizingthe difference density matrix.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.
  	Alias names for this keyword: COUPLING_METRIC
  	This keyword cites the following reference: [Mavros2015]

  MORE_WORK
  	MORE_WORK {Integer}
  	Control parameter for dynamic load balancing during a mixed CDFT calculation. See code for details.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0

  NONORTHOGONAL_COUPLING
  	NONORTHOGONAL_COUPLING {Logical}
  	Print out the nonorthogonal diabatic CDFT coupling between states, as it appears in the mixed CDFT Hamiltonian before orthogonalization (coupling calculations) and CDFT-CI. Useful for (re)constructing the Hamiltonian for additionalanalysis. This is the CDFT interaction energy between states.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.
  	Alias names for this keyword: NONORTHO_COUPLING

  SCALE_WITH_OCCUPATION_NUMBERS
  	SCALE_WITH_OCCUPATION_NUMBERS {Logical}
  	Scale molecular orbitals with occupation numbers before calculating the electronic coupling. Affects only simulations which employ MO smearing. Disabling this keyword in conjunction with a properly selected EPS_OCCUPIED threshold might be useful in systems with a large number of fractionally occupied orbitals.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .TRUE.

  VERY_OVERLOADED
  	VERY_OVERLOADED {Real}
  	Control parameter for dynamic load balancing during a mixed CDFT calculation. See code for details.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+000

  WFN_OVERLAP
  	WFN_OVERLAP {Logical}
  	Compute the CDFT electronic coupling element using the wavefunction overlap method in addition to the standard method defined by the keyword COUPLING. In this method, the unconstrained KS ground state wavefunction (WFN_RESTART_FILE_NAME) is represented as a linear combination of the CDFT states. For more than two CDFT states, the coupling is computed pairwise for every state pair (contrary to other coupling methods).
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.
  	This keyword cites the following reference: [Migliore2009]

  WFN_RESTART_FILE_NAME
  	WFN_RESTART_FILE_NAME {String}
  	Name of the wavefunction restart file that defines the unconstrained KS ground state, which is used to compute the electronic coupling with the wavefunction overlap method. May include a path.
  	This keyword cannot be repeated and it expects precisely one string.