The following two $rem variables must be specified in order to run HF calculations:
METHOD
METHOD
Specifies the exchange-correlation functional.
TYPE:
STRING
DEFAULT:
No default
OPTIONS:
NAME
Use METHOD = NAME, where NAME is one of the following:
HF for Hartree-Fock theory;
one of the DFT methods listed in Section 5.3.5.;
one of the correlated methods listed in Sections 7.10,
7.11, and 7.9;
RECOMMENDATION:
In general, consult the literature to guide your selection. Our recommendations for DFT are indicated
in bold in Section 5.3.5.
BASIS
BASIS
Specifies the basis sets to be used.
TYPE:
STRING
DEFAULT:
No default basis set
OPTIONS:
General, Gen
User defined ($basis keyword required).
Symbol
Use standard basis sets as per Chapter 8.
Mixed
Use a mixture of basis sets (see Chapter 8).
RECOMMENDATION:
Consult literature and reviews to aid your selection.
In addition, the following $rem variables can be used to customize the SCF calculation:
GEN_SCFMAN
GEN_SCFMAN
Use GEN_SCFMAN for the present SCF calculation.
TYPE:
BOOLEAN
DEFAULT:
TRUE
OPTIONS:
FALSE
Use the previous SCF code.
TRUE
Use GEN_SCFMAN.
RECOMMENDATION:
Set to FALSE in cases where features not yet supported by GEN_SCFMAN are needed.
ORBITAL_ENERGY_PREC
ORBITAL_ENERGY_PREC
Obtain additional digits of precision in the orbital energies.
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
0
Standard printout with 4 decimal digits (in Hartree).
1
5 decimal digits.
2
Scientific notation with 10 digits of precision.
RECOMMENDATION:
Set as desired. Has no effect in cases where the orbital symmetry labels are printed;
use SYM_IGNORE = TRUE if additional precision is needed in such cases.
PRINT_ORBITALS
PRINT_ORBITALS
Prints orbital coefficients with atom labels in analysis part of output.
TYPE:
INTEGER/LOGICAL
DEFAULT:
FALSE
OPTIONS:
FALSE
Do not print any orbitals.
TRUE
Prints occupied orbitals plus 5 virtual orbitals.
NVIRT
Number of virtual orbitals to print.
RECOMMENDATION:
Use true unless more virtual orbitals are desired.
SCF_CONVERGENCE
SCF_CONVERGENCE
SCF is considered converged when the wave function error is less that
. Adjust the value of THRESH at the same time.
TYPE:
INTEGER
DEFAULT:
5
For single point energy calculations (including BSSE and XSAPT jobs).
7
For job types NMR, STATPOLAR, DYNPOLAR, HYPERPOLAR, and ISSC.
8
For most other job types, including geometry optimization, transition-state search,
vibrational analysis, CIS/TDDFT calculations, correlated wavefunction methods,
energy decomposition analysis (EDA2), etc.
OPTIONS:
User-defined
RECOMMENDATION:
Tighter criteria are recommended for geometry optimization and vibration analysis. Larger
values provide more significant figures, at greater computational cost. Beginning
with Q-Chem 3.0, the DIIS error is measured by the maximum error
rather than the RMS error that was used in earlier versions.
UNRESTRICTED
UNRESTRICTED
Controls the use of restricted or unrestricted orbitals.
TYPE:
LOGICAL
DEFAULT:
FALSE
Closed-shell systems.
TRUE
Open-shell systems.
OPTIONS:
FALSE
Constrain the spatial part of the alpha and beta orbitals to be the same.
TRUE
Do not Constrain the spatial part of the alpha and beta orbitals.
RECOMMENDATION:
Use the default unless ROHF is desired. Note that for unrestricted calculations on
systems with an even number of electrons it is usually necessary to break
/ symmetry in the initial guess, by using SCF_GUESS_MIX or
providing $occupied information (see Section 4.4 on initial guesses).
The calculations using other more special orbital types are controlled by the following $rem variables (they are not effective if GEN_SCFMAN = FALSE):
OS_ROSCF
OS_ROSCF
Run an open-shell singlet ROSCF calculation with GEN_SCFMAN.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
OS_ROSCF calculation is performed.
FALSE
Do not run OS_ROSCF (it will run a closed-shell RSCF calculation instead).
RECOMMENDATION:
Set to TRUE if desired.
ROSCF_DODS
ROSCF_DODS
Run a canonical restricted open-shell calculation (also called “ROSCF-DODS”,
where DODS stands for different orbitals for different spins) with
GEN_SCFMAN. Available for high-spin half-filled open-shell systems.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Perform a canonical ROSCF calculation.
FALSE
Do not perform a canonical ROSCF calculation (run an open-shell USCF
calculation instead).
RECOMMENDATION:
Set to TRUE if desired.
GHF
GHF
Run a generalized Hartree-Fock calculation with GEN_SCFMAN.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Run a GHF calculation.
FALSE
Do not use GHF.
RECOMMENDATION:
Set to TRUE if desired.
COMPLEX
COMPLEX
Run an SCF calculation with complex MOs using GEN_SCFMAN.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Use complex orbitals.
FALSE
Use real orbitals.
RECOMMENDATION:
Set to TRUE if desired.
COMPLEX_MIX
COMPLEX_MIX
Mix a certain percentage of the real part of the HOMO to the
imaginary part of the LUMO.
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
0–100
The mix angle = COMPLEX_MIX/100.
RECOMMENDATION:
It may help find the stable complex solution (similar idea as SCF_GUESS_MIX).
Example 4.1 Restricted open-shell singlet ROSCF calculation for the first excited state of formaldehyde using GEN_SCFMAN. The first job provides the guess orbitals through a restricted SCF calculation.
$molecule 0 1 H -0.940372 0.000000 1.268098 H 0.940372 0.000000 1.268098 C 0.000000 0.000000 0.682557 O 0.000000 0.000000 -0.518752 $end $rem GEN_SCFMAN true METHOD wb97x-d BASIS def2-svpd THRESH 14 SCF_CONVERGENCE 9 point_group_symmetry False $end @@@ $molecule read $end $rem JOBTYPE sp METHOD wb97x-d BASIS def2-svpd GEN_SCFMAN true OS_ROSCF true THRESH 14 SCF_CONVERGENCE 9 SCF_ALGORITHM diis point_group_symmetry False SCF_GUESS read $end