4.3.2 Job Control

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
       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.

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.

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 is considered converged when the wave function error is less that ${10}^{-\mathrm{SCF}\mathrm{\_}\mathrm{CONVERGENCE}}$. Adjust the value of THRESH at the same time. (Starting with Q-Chem 3.0, the DIIS error is measured by the maximum error rather than the RMS error as in earlier versions.)
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 for geometry optimization and vibration analysis. Larger values provide more significant figures, at greater computational cost.

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 $\alpha$/$\beta$ symmetry in the initial guess, by using SCF_GUESS_MIX or providing $occupied information (see Section 4.4 on initial guesses).

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 close-shell RSCF calculation instead).
RECOMMENDATION:
       Set to TRUE if desired.

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
       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
       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 = $\pi \cdot$COMPLEX_MIX/100.
RECOMMENDATION:
       It may help find the stable complex solution (similar idea as SCF_GUESS_MIX).