hessian

psi4.driver.hessian(name, **kwargs)

Function complementary to frequency(). Computes force constants, deciding analytic, finite difference of gradients, or finite difference of energies.

Returns:Matrix – Total non-mass-weighted electronic Hessian in Hartrees/Bohr/Bohr. Returns:(Matrix, Wavefunction) – Hessian and wavefunction when return_wfn specified. Examples:

>>> # [1] Frequency calculation without thermochemical analysis
>>> hessian('mp3')

>>> # [2] Frequency calc w/o thermo analysis getting the Hessian
>>> #     in file, core.Matrix, and np.array forms
>>> set hessian_write on
>>> H, wfn = hessian('ccsd', return_wfn=True)
>>> wfn.hessian().print_out()
>>> np.array(H)