# Notes on Options

Note

The options referred to in the Theoretical Methods: SCF to FCI section below and indexed in Keywords by Module are placed in `set` blocks as described in Job Control Keywords, not as arguments to a Python function (like `energy()`).

Note

All PSI4 keyword names and values are insensitive to case, both those that are placed in `set` blocks and as Python function arguments. The few exceptions are documented for the `database()` function, where case structure must match the database file.

Note

Boolean options can be specified by `yes`, `on`, `true`, or `1` for affirmative and `no`, `off`, `false`, or `0` for negative, all insensitive to case.

Note

Certain convergence and tolerance keywords, of type double (real numbers), may be specified using either a real number or an integer; and integer X is then treated as the number of converged decimal digits required. For example, to request as energy converged to \(10^{-6} E_h\), the user may set the `e_convergence` keyword to `0.000001`, `1.0e-6`, or `6`.

# Alternate Implementations

Depending on the reference (RHF, UHF, ROHF) and the integral treatment (conventional CONV, density-fitted DF, and Cholesky-decomposed CD), computational methods are sometimes implemented by multiple coders or even multiple times. PSI4 transparently selects the most efficient implementation, so one generally needn’t consult this table. However, to understand the details of what combinations are accessible or what alternate implementations are available, read on.

Below, “Y” means method available in module, “D” means module is default for that method, and “” means method not available. HF, DFT, and MP2 default to density-fitted integrals, while all higher methods default to conventional integrals. Therefore, for a closed-shell molecule:

- runs MP2 with default `DF` with default implementation DFMP2

      1

      energy('mp2')

- runs MP2 with `CONV` with default implementation OCC

      1
      2

      set mp2_type conv
      energy('mp2')

- runs MP2 with default `DF` with implementation OCC

      1
      2

      set qc_module occ
      energy('mp2')

Overlapping capabilities of PSI4. “Y” is available; “D” is default.
name _ type select [1] | QC_MODULE REFERENCE _ | `energy()` | `gradient()`
--- | --- | --- | ---
RHF | UHF | ROHF | RHF | UHF | ROHF
CV | DF | CD | CV | DF | CD | CV | DF | CD | CV | DF | CD | CV | DF | CD | CV | DF | CD
mp2 MP2_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI | Y |  |  |  |  |  | Y |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  | D [2] |  |  | D [2] |  |  | D |  |  | D |  |  |  |  |  |  |
FNOCC | Y |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC | D | Y | D | D | Y | Y | D | Y | D | D | Y |  | D | D |  |  |  |
mp3 MP_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI | Y |  |  |  |  |  | Y [3] |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | Y |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC | D | D | D | D | D | D |  |  |  | D | D |  | D | D |  |  |  |
mp2.5 MP_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC | D | D | D | D | D | D |  |  |  | D | D |  | D | D |  |  |  |
mp4 MP_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI | Y |  |  |  |  |  | Y [3] |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
lccd CC_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC | Y | D | D | D | D | D |  |  |  | D | D |  | D | D |  |  |  |
lccsd, cepa(0) CC_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ccsd CC_TYPE | CCENERGY | D |  |  | D |  |  | D |  |  | D |  |  | D |  |  | D |  |
DETCI |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | Y | D | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC |  | Y | Y |  |  |  |  |  |  |  | D |  |  |  |  |  |  |
ccsd(t) CC_TYPE | CCENERGY | D |  |  | D |  |  | D |  |  | D |  |  | D |  |  |  |  |
DETCI |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | Y | D | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC |  | Y | Y |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ccsd(at) CC_TYPE | CCENERGY | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC |  | D | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
cisd CI_TYPE | CCENERGY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
DETCI | Y |  |  |  |  |  | D |  |  |  |  |  |  |  |  |  |  |
DFMP2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNOCC | D |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OCC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

Footnotes

[1] | Algorithm type selection keyword below. Values to the right: conventional `CONV` (here abbreviated CV), density-fitted `DF`, and Cholesky-decomposed `CD`.

[2] | (1, 2) Also available for KS reference.

[3] | (1, 2) Conditions have no default module (computationally inefficient) and can only be accessed by specifying QC_MODULE.