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Table of contents

• Table of contents
• Details
• Keywords
  • The REFERENCE Keyword
    • DFT Functionals
  • The JOB Keyword
  • The X2CTYPE Keyword
• Examples
  • Restricted Hartree-Fock Energy
  • Unrestricted Kohn-Sham (B3LYP) Response
  • Complex Generalized Kohn-Sham (LSDA) Energy
  • Relativistic Kohn-Sham (BHandH) Electron Dynamics

Details

The QM section handles the reference and ChronusQ job type specification. The QM section is a required section for all ChronusQ jobs.

Keywords

Keyword	Type	Description	Default	Required
REFERENCE	String	Type of reference wavefunction	N/A	Yes
JOB	String	Type of calculation	N/A	Yes
X2CTYPE	String	Type of X2C transformation	FULL	No

The REFERENCE Keyword

The QM.REFERENCE keyword allows for specification of the reference wave function for SCF and post-SCF ChronusQ calculations. ChronusQ currently supports Hartree-Fock and Kohn-Sham reference choices. The REFERENCE keyword may be constructed systematically as

REFERENCE = [ REAL/COMPLEX ] <R/RO/U/G/2C><HF/FUNCTIONAL>

The REAL/COMPLEX specification is optional, and a canonical choice will be chosen for the user should it not be specified (COMPLEX for 2-Component / GIAO references, REAL otherwise). The second two keyword fields in the above template are required, and may be combined freely.

R/RO/U/G/X2C specifies the desired spin symmetry of the reference wave function: Restricted (S² eigenfunction, even number of particles), Restricted Open (S² eigenfunction, any number of particles), Unrestricted (S_z eigenfunction), Generalized (2-Component, no spin symmetry), X2C ("Exact" 2-Component Relativistic, with one-body spin-orbit coupling, no spin symmetry), respectively.

HF will generate a Hartree-Fock wave function, and FUNCTIONAL is a place holder to specify a Kohn-Sham wave function with the FUNCTIONAL DFT functional. (See below) RO is currently only compatible with HF, not Kohn-Sham.

DFT Functionals

ChronusQ supports the following DFT functionals (10/9/2020):

Name	Type	Description
SLATER	Pure LDA Exchange	Slater exchange
LSDA/LDA	Pure LDA Exchange/Correlation	Slater exchange + VWN3 correlation
SVWN5	Pure LDA Exchange/Correlation	Slater exchange + VWN5 correlation
B88	Pure GGA Exchange	B88 exchange
BLYP	Pure GGA Exchange/Correlation	B88 exchange + LYP correlation
PBEXPBEC	Pure GGA Exchange/Correlation	PBE exchange + PBE correlation
B3LYP	Hybrid GGA Exchange/Correlation	B3LYP functional
B3PW91	Hybrid GGA Exchange/Correlation	B3PW91 functional
PBE0	Hybrid GGA Exchange/Correlation	PBE0 functional
BHANDHLYP	Hybrid GGA Exchange/Correlation	BHandHLYP functional
BHANDH	Hybrid GGA Exchange/Correlation	BHandH functional

Addition of more functionals is possible - if a specific functional is required for your research, please open an issue!

The JOB Keyword

The JOB keyword controls the type of calculation done by ChronusQ. The currently supported job types are:

Value	Description
SCF	Self-consistent orbital optimization
RESP	Response theory
RT	Electron dynamics

For more information, see the respective input sections of each.

The X2CTYPE Keyword

When the reference is specified as X2C, different methodologies can be used to define the transformation between the four- and two-component Hamiltonians. The X2CTYPE keyword controls the type of transform used.

Value	Description
FULL	The standard X2C transformation algorithm without local approximation
ALH	Atomic local approximation to the Hamiltonian
ALU	Atomic local approximation to the transformation matrix
DLH	Diagonal local approximation to the Hamiltonian
DLU	Diagonal local approximation to the transformation matrix
SO	Include spin-orbit relativistic effect in X2C
SCALAR	Only compute scalar relativistic effect in X2C

Examples

Restricted Hartree-Fock Energy

[QM]
Reference = RHF
Job = SCF

Unrestricted Kohn-Sham (B3LYP) Response

[QM]
Reference = UB3LYP
Job = Resp

Complex Generalized Kohn-Sham (LSDA) Energy

[QM]
Reference = Complex GLSDA
Job = SCF

Relativistic Kohn-Sham (BHandH) Electron Dynamics

[QM]
Reference = X2CBHandH
Job = RT