# Energy

`energy`(name[, bypass_scf, molecule])

  Function to compute the single-point electronic energy.

  Returns: | (float) Total electronic energy in Hartrees. SAPT returns interaction energy.
  PSI variables: |

  - `CURRENT ENERGY`
  - `CURRENT REFERENCE ENERGY`
  - `CURRENT CORRELATION ENERGY`

  name | calls method DFT [manual]
  --- | ---
  b2plyp | B2PLYP Double Hybrid Exchange-Correlation Functional
  b2plyp-d | B2PLYP Double Hybrid Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  b2plyp-d3 | B2PLYP Double Hybrid Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  b2plyp-d3bj | B2PLYP Double Hybrid Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  b3lyp | B3LYP Hybrid-GGA Exchange-Correlation Functional
  b3lyp-chg | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Chai and Head-Gordon Dispersion Correction
  b3lyp-d | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  b3lyp-d1 | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Grimme’s -D1 Dispersion Correction
  b3lyp-d3 | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  b3lyp-d3bj | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  b3_x | Becke88 GGA Exchange (B3LYP weighting)
  b88_x | Becke88 GGA Exchange
  b97-0 | B97-0 Hybrid-GGA Exchange-Correlation Functional
  b97-1 | B97-1 Hybrid-GGA Exchange-Correlation Functional
  b97-2 | B97-2 Hybrid-GGA Exchange-Correlation Functional
  b97-d | B97-D Pure-GGA Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  b97-d3 | B97-D Pure-GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  b97-d3bj | B97-D Pure-GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  blyp | BLYP GGA Exchange-Correlation Functional
  blyp-d | BLYP GGA Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  blyp-d1 | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Grimme’s -D1 Dispersion Correction
  blyp-d3 | BLYP GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  blyp-d3bj | BLYP GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  bp86 | BP86 GGA Exchange-Correlation Functional
  bp86-d | BP86 GGA Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  bp86-d1 | B3LYP Hybrid-GGA Exchange-Correlation Functional w/ Grimme’s -D1 Dispersion Correction
  bp86-d3 | BP86 GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  bp86-d3bj | BP86 GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  ft97 | FT97 GGA Exchange-Correlation Functional
  ft97b_x | Filitov and Theil 1997 Exchange
  ft97_c | FT97 Correlation (Involves Ei functions)
  hcth | HCTH Pure-GGA Exchange-Correlation Functional
  hcth120 | HCTH120 Pure-GGA Exchange-Correlation Functional
  hcth120-d3 | HCTH120 Pure-GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  hcth120-d3bj | HCTH120 Pure-GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  hcth147 | HCTH147 Pure-GGA Exchange-Correlation Functional
  hcth407 | HCTH407 Pure-GGA Exchange-Correlation Functional
  hf+d | w/ Podeszwa and Szalewicz Dispersion Correction
  lyp_c | LYP Correlation
  m05 | Heavily Parameterized Hybrid Meta-GGA XC Functional
  m05-2x | Heavily Parameterized Hybrid Meta-GGA XC Functional
  m05-2x-d3 | Heavily Parameterized Hybrid Meta-GGA XC Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  m05-d3 | Heavily Parameterized Hybrid Meta-GGA XC Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  p86_c | P86 Correlation (PZ81 LSDA + P86 GGA)
  pbe | PBE GGA Exchange-Correlation Functional
  pbe-d | PBE GGA Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  pbe-d1 | PBE GGA Exchange-Correlation Functional w/ Grimme’s -D1 Dispersion Correction
  pbe-d3 | PBE GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  pbe-d3bj | PBE GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  pbe0 | PBE0 Hybrid GGA Exchange-Correlation Functional
  pbe0-2 | PBE0-2 Double Hydrid Exchange-Correlation Functional
  pbe0-d | PBE0 Hybrid GGA Exchange-Correlation Functional w/ Grimme’s -D2 Dispersion Correction
  pbe0-d3 | PBE0 Hybrid GGA Exchange-Correlation Functional w/ Grimme’s -D3 (zero-damping) Dispersion Correction
  pbe0-d3bj | PBE0 Hybrid GGA Exchange-Correlation Functional w/ Grimme’s -D3 (BJ-damping) Dispersion Correction
  pbea_c | New Implementation of PBEC in wPBEc-sr.
  pbesol_x | PBEsol GGA Exchange Hole (Parameter Free)
  pbe_c | PBE Correlation
  pbe_x | PBE GGA Exchange Hole (Parameter Free)
  pw91 | PW91 GGA Exchange-Correlation Functional
  pw91_c | PW91 Correlation
  pw91_x | PW91 Parameterized GGA Exchange
  pw92a_c | New Implementation of PW92C in wPBEc-sr.
  pw92_c |
  pz81_c | PZ81 Correlation
  rpbe_x | RPBE GGA Exchange Hole (Parameter Free)
  sogga | Second Order GGA Exchange-Correlation Functional
  sogga_x | Second Order GGA Exchange Hole (Parameter Free)
  svwn | SVWN3 (RPA) LSDA Functional
  s_x | Slater LSDA Exchange
  vwn3rpa_c | VWN3 (RPA) LSDA Correlation
  vwn3_c | VWN3 LSDA Correlation
  vwn5rpa_c | VWN5 (RPA) LSDA Correlation
  vwn5_c | VWN5 LSDA Correlation
  dldf | Dispersionless Hybrid Meta-GGA XC Functional
  dldf+d | Dispersionless Hybrid Meta-GGA XC Functional w/ Podeszwa and Szalewicz Dispersion Correction
  dldf+d09 | Dispersionless Hybrid Meta-GGA XC Functional w/ Podeszwa and Szalewicz Dispersion Correction
  wb88_x | B88 Short-Range GGA Exchange (HJS Model)
  wb97 | Parameterized LRC B97 GGA XC Functional
  wb97x | Parameterized Hybrid LRC B97 GGA XC Functional
  wb97x-d | Parameterized Hybrid LRC B97 GGA XC Functional with Dispersion w/ Chai and Head-Gordon Dispersion Correction
  wblyp | BLYP SR-XC Functional (HJS Model)
  wpbe | PBE SR-XC Functional (HJS Model)
  wpbe0 | PBE0 SR-XC Functional (HJS Model)
  wpbe2 | Double-Hybrid PBE LRC Functional
  wpbe_c | Short-Range PBE Correlation Functional
  wpbe_x | PBE Short-Range GGA Exchange (HJS Model)
  wpbesol | PBEsol SR-XC Functional (HJS Model)
  wpbesol0 | PBEsol0 SR-XC Functional (HJS Model)
  wpbesol_x | PBEsol Short-Range GGA Exchange (HJS Model)
  wpw92_c | Short-Range PW92 Correlation Functional
  wsvwn | LSDA SR-XC Functional
  ws_x | Slater Short-Range LSDA Exchange

  > name | calls method in Kallay’s MRCC program [manual]
  > --- | ---
  > mrccsd | CC through doubles
  > mrccsdt | CC through triples
  > mrccsdtq | CC through quadruples
  > mrccsdtqp | CC through quintuples
  > mrccsdtqph | CC through sextuples
  > mrccsd(t) | CC through doubles with perturbative triples
  > mrccsdt(q) | CC through triples with perturbative quadruples
  > mrccsdtq(p) | CC through quadruples with pertubative quintuples
  > mrccsdtqp(h) | CC through quintuples with pertubative sextuples
  > mrccsd(t)_l |
  > mrccsdt(q)_l |
  > mrccsdtq(p)_l |
  > mrccsdtqp(h)_l |
  > mrccsdt-1a | CC through doubles with iterative triples (cheapest terms)
  > mrccsdtq-1a | CC through triples with iterative quadruples (cheapest terms)
  > mrccsdtqp-1a | CC through quadruples with iterative quintuples (cheapest terms)
  > mrccsdtqph-1a | CC through quintuples with iterative sextuples (cheapest terms)
  > mrccsdt-1b | CC through doubles with iterative triples (cheaper terms)
  > mrccsdtq-1b | CC through triples with iterative quadruples (cheaper terms)
  > mrccsdtqp-1b | CC through quadruples with iterative quintuples (cheaper terms)
  > mrccsdtqph-1b | CC through quintuples with iterative sextuples (cheaper terms)
  > mrcc2 | approximate CC through doubles
  > mrcc3 | approximate CC through triples
  > mrcc4 | approximate CC through quadruples
  > mrcc5 | approximate CC through quintuples
  > mrcc6 | approximate CC through sextuples
  > mrccsdt-3 | CC through doubles with iterative triples (all but the most expensive terms)
  > mrccsdtq-3 | CC through triples with iterative quadruples (all but the most expensive terms)
  > mrccsdtqp-3 | CC through quadruples with iterative quintuples (all but the most expensive terms)
  > mrccsdtqph-3 | CC through quintuples with iterative sextuples (all but the most expensive terms)

  > name | calls method in Stanton and Gauss’s CFOUR program [manual]
  > --- | ---
  > c4-scf | Hartree–Fock (HF)
  > c4-mp2 | 2nd-order Moller-Plesset perturbation theory (non-density-fitting) (MP2)
  > c4-mp3 | 3rd-order Moller-Plesset perturbation theory (MP3)
  > c4-mp4(sdq) | 4th-order MP perturbation theory (MP4) less triples
  > c4-mp4 | full MP4
  > c4-cc2 | approximate coupled cluster singles and doubles (CC2)
  > c4-ccsd | coupled cluster singles and doubles (CCSD)
  > c4-cc3 | approximate CC singles, doubles, and triples (CC3)
  > c4-ccsd(t) | CCSD with perturbative triples (CCSD(T))
  > c4-ccsdt | coupled cluster singles, doubles, and triples (CCSDT)
  > cfour | expert full control over cfour program

  Parameters:

  - name (string) –

    `'scf'` || `'df-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.

  Parameters: | bypass_scf (boolean) – `'on'` || `'off'` Indicates whether, for name values built atop of scf calculations, the scf step is skipped. Suitable when special steps are taken to get the scf to converge in an explicit preceeding scf step.
  Examples: |

      >>> # [1] Coupled-cluster singles and doubles calculation with psi code
      >>> energy('ccsd')

      >>> # [2] Charge-transfer SAPT calculation with scf projection from small into
      >>> #     requested basis, with specified projection fitting basis
      >>> set basis_guess true
      >>> set df_basis_guess jun-cc-pVDZ-JKFIT
      >>> energy('sapt0-ct')

      >>> # [3] Arbitrary-order MPn calculation
      >>> energy('mp4')

      >>> # [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 global basis cc-pVDZ
      >>> set global reference rohf
      >>> energy('scf')
      >>> H2.set_multiplicity(3)
      >>> psi4.MintsHelper().integrals()
      >>> energy('detci', bypass_scf=True)

      >>> # [5] Run two CI calculations, keeping the integrals generated in the first one.
      >>> molecule ne {\\nNe\\n}
      >>> set globals  basis cc-pVDZ
      >>> set transqt2 delete_tei false
      >>> energy('cisd')
      >>> energy('fci', bypass_scf='True')