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# 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, 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 , the user may set the `e_convergence` keyword to 0.000001, 1.0e-6, or 6.

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