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QM

Table of contents

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 (Sz 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