Section XAS

• Sets the method of choice to calculate core-level excitation spectra. The occupied states from which we calculate the excitation should be specified. Localization of the orbitals may be useful.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / XAS

• This section cannot be repeated.

• This section cites the following reference: [Iannuzzi2007]

• Subsections

  • LOCALIZE
  • PRINT
  • SCF

• Keywords

  • SECTION_PARAMETERS
  • ADDED_MOS
  • ATOMS_LIST
  • DIPOLE_FORM
  • EPS_ADDED
  • MAX_ITER_ADDED
  • METHOD
  • NGAUSS
  • ORBITAL_LIST
  • OVERLAP_THRESHOLD
  • RESTART
  • SPIN_CHANNEL
  • STATE_SEARCH
  • STATE_TYPE
  • WFN_RESTART_FILE_NAME
  • XAS_CORE
  • XAS_TOT_EL
  • XES_CORE
  • XES_EMPTY_HOMO

• Keyword descriptions

  SECTION_PARAMETERS
  	&XAS {Logical}
  	controls the activation of core-level spectroscopy simulations
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ADDED_MOS
  	ADDED_MOS {Integer}
  	Number of additional MOS added spin up only
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: -1

  ATOMS_LIST
  	ATOMS_LIST {Integer} ... or a range {Integer}..{Integer}
  	Indexes of the atoms to be excited. This keyword can be repeated several times(useful if you have to specify many indexes).
  	This keyword can be repeated and it expects a list of integers.
  	Alias names for this keyword: AT_LIST

  DIPOLE_FORM
  	DIPOLE_FORM {Keyword}
  	Type of integral to get the oscillator strengths in the diipole approximation
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: VELOCITY
  	List of valid keywords: LENGTH Length form 〈 i | e r | j 〉 VELOCITY Velocity form 〈 i | d/dr | j 〉
  	Alias names for this keyword: DIP_FORM

  EPS_ADDED
  	EPS_ADDED {Real}
  	target accuracy incalculation of the added orbitals
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-005

  MAX_ITER_ADDED
  	MAX_ITER_ADDED {Integer}
  	maximum number of iteration in calculation of added orbitals
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 2999

  METHOD
  	METHOD {Keyword}
  	Method to be used to calculate core-level excitation spectra
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: NONE
  	List of valid keywords: DSCF DSCF calculations to compute the first (core)excited state NONE No core electron spectroscopy TP_FH Transition potential full-hole TP_FLEX Transition potential with generalized core occupation and total number of electrons TP_HH Transition potential half-hole TP_VAL Hole in homo for X-ray emission only TP_XFH Transition potential excited full-hole TP_XHH Transition potential excited half-hole
  	Alias names for this keyword: XAS_METHOD

  NGAUSS
  	NGAUSS {Integer}
  	Number of gto's for the expansion of the STO of the type given by STATE_TYPE
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 3

  ORBITAL_LIST
  	ORBITAL_LIST {Integer} ... or a range {Integer}..{Integer}
  	Indices of the localized orbitals to be excited. This keyword can be repeated several times(useful if you have to specify many indexes).
  	This keyword can be repeated and it expects a list of integers.
  	Alias names for this keyword: ORBITAL_LIST

  OVERLAP_THRESHOLD
  	OVERLAP_THRESHOLD {Real}
  	Threshold for including more than one initial core excited state per atom. The threshold is taken relative to the maximum overlap.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+000

  RESTART
  	RESTART {Logical}
  	Restart the excited state if the restart file exists
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  SPIN_CHANNEL
  	SPIN_CHANNEL {Integer}
  	# Spin channel of the excited orbital
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 1

  STATE_SEARCH
  	STATE_SEARCH {Integer}
  	# of states where to look for the one to be excited
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: -1

  STATE_TYPE
  	STATE_TYPE {Keyword}
  	Type of the orbitals that are excited for the xas spectra calculation
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: 1S
  	List of valid keywords: 1S 1s orbitals 2P 2p orbitals 2S 2s orbitals 3D 3d orbitals 3P 3p orbitals 3S 3s orbitals 4D 4d orbitals 4F 4f orbitals 4P 4p orbitals 4S 4s orbitals
  	Alias names for this keyword: TYPE

  WFN_RESTART_FILE_NAME
  	WFN_RESTART_FILE_NAME {String}
  	Root of the file names where to read the MOS from which to restart the calculation of the core level excited states
  	This keyword cannot be repeated and it expects precisely one string.
  	Alias names for this keyword: RESTART_FILE_NAME

  XAS_CORE
  	XAS_CORE {Real}
  	Occupation of the core state in XAS calculation by TP_FLEX.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-001

  XAS_TOT_EL
  	XAS_TOT_EL {Real}
  	Total number of electrons for spin channel alpha, in XAS calculation by TP_FLEX.If it is a negative value, the number of electrons is set to GS number of electrons minus the amount subtracted from the core state
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: -1.00000000E+000

  XES_CORE
  	XES_CORE {Real}
  	Occupation of the core state in XES calculation by TP_VAL. The HOMO is emptied by the same amount.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+000

  XES_EMPTY_HOMO
  	XES_EMPTY_HOMO {Logical}
  	Set the occupation of the HOMO in XES calculation by TP_VAL. The HOMO can be emptied or not, if the core is still full.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.