SinglePoint Energy — energy()
¶
 Psi4 Native Energy Methods
 Psi4 Native DFT Energy Methods
 MRCC Interfaced Energy Methods
 CFOUR Interfaced Energy Methods

psi4.
energy
(name[, molecule, return_wfn, restart_file])[source]¶ Function to compute the singlepoint electronic energy.
Returns: float – Total electronic energy in Hartrees. SAPT & EFP return interaction energy. Returns: (float, Wavefunction
) – energy and wavefunction when return_wfn specified.PSI variables: Parameters:  name (string) –
'scf'
'mp2'
'ci5'
 etc.First argument, usually unlabeled. Indicates the computational method to be applied to the system.
 molecule (molecule) –
h2o
 etc.The target molecule, if not the last molecule defined.
 return_wfn (boolean) –
'on'
 \(\Rightarrow\)'off'
\(\Leftarrow\)Indicate to additionally return the
Wavefunction
calculation result as the second element (after float energy) of a tuple.  restart_file (string) –
['file.1, file.32]
./file
 etc.Binary data files to be renamed for calculation restart.
Examples: >>> # [1] Coupledcluster singles and doubles calculation with psi code >>> energy('ccsd')
>>> # [2] Chargetransfer SAPT calculation with scf projection from small into >>> # requested basis, with specified projection fitting basis >>> set basis_guess true >>> set df_basis_guess junccpVDZJKFIT >>> energy('sapt0ct')
>>> # [3] Arbitraryorder MPn calculation >>> energy('mp7')
>>> # [4] Converge scf as singlet, then run detci as triplet upon singlet reference >>> # Note that the integral transformation is not done automatically when detci is run in a separate step. >>> molecule H2 {\n0 1\nH\nH 1 0.74\n} >>> set basis ccpVDZ >>> set reference rohf >>> scf_e, scf_wfn = energy('scf', return_wfn=True) >>> H2.set_multiplicity(3) >>> core.MintsHelper(scf_wfn.basisset()).integrals() >>> energy('detci', ref_wfn=scf_wfn)
>>> # [5] Run two CI calculations, keeping the integrals generated in the first one. >>> molecule ne {\nNe\n} >>> set basis ccpVDZ >>> cisd_e, cisd_wfn = energy('cisd', return_wfn=True) >>> energy('fci', ref_wfn=cisd_wfn)
>>> # [6] Can automatically perform complete basis set extrapolations >>> energy("CCSD/ccpV[DT]Z")
>>> # [7] Can automatically perform delta corrections that include extrapolations >>> # even with a userdefined extrapolation formula. See sample inputs named >>> # cbsxtpl* for more examples of this input style >>> energy("MP2/augccpv([d,t]+d)z + d:ccsd(t)/ccpvdz", corl_scheme=myxtplfn_2)
 name (string) –