Polar Keyword
Last Update: 12/31/2000

This method keyword requests that the dipole electric field polarizabilities (and hyperpolarizabilities, if possible) be computed. No geometry change or derivatives are implied, but this keyword may be combined in the same job with numerical differentiation of forces by specifying both Freq and Polar in the route section. Freq and Polar may not be combined for methods lacking analytic gradients (MP4(SDTQ), QCISD(T), CCSD(T), BD, and so on). Note that Polar is done by default when second derivatives are computed analytically.

Step=N
Specifies the step size in the electric field to be 0.0001N atomic units.

Analytic
Compute polarizability and hyperpolarizability analytically. This is possible for RHF, UHF, and MP2, for which it is the default. The polarizability is always computed during analytic frequency calculations.

Numerical
Computes the polarizability as a numerical derivative of the dipole moment (itself the analytic derivative of the energy, of course, not the expectation value in the case of MP2 or CI energies). The default for methods for which only analytic first derivatives are available.

EnOnly
Requests double numerical differentiation of energies to produce polarizabilities. EnergyOnly, a synonym for EnOnly, is a misnomer, since analytic first derivatives will also be differentiated twice, to produce hyperpolarizabilities, when they are available.

Restart
Restarts a numerical polarizability calculation from the checkpoint file. A failed Polar calculation may be restarted from its checkpoint file by simply repeating the route section of the original job, adding the Restart option to the Polar keyword. No other input is required.

Dipole
Compute the dipole polarizabilities (this is the default).

Polarizabilities and hyperpolarizabilities will be automatically computed for HF, all DFT methods, and MP2. Polar will compute polarizabilities only, and Polar=EnOnly will produce both polarizabilities and hyperpolarizabilities for CIS, MP2, MP3, MP4(SDQ), CID, CISD, CCD, QCISD, and CASSCF. Polar will produce only polarizabilities for all other methods (for which no analytic derivatives are available, making EnOnly the default). Note that Polar is not available for any semi-empirical method.

Freq

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