Function to compute the singlepoint electronic energy.
Returns:  (float) Total electronic energy in Hartrees. SAPT returns interaction energy. 

Psi variables: 
name  calls method 

scf  Hartree–Fock (HF) or density functional theory (DFT) [manual] 
dcft  density cumulant functional theory [manual] 
mcscf  multiconfigurational self consistent field (SCF) 
mp2  2ndorder MollerPlesset perturbation theory (MP2) [manual] 
dfmp2  MP2 with density fitting [manual] 
convmp2  conventional MP2 (nondensityfitting) [manual] 
mp3  3rdorder MollerPlesset perturbation theory (MP3) [manual] 
mp2.5  average of MP2 and MP3 [manual] 
mp4(sdq)  4thorder MP perturbation theory (MP4) less triples [manual] 
mp4  full MP4 [manual] 
mpn  nthorder Moller–Plesset (MP) perturbation theory [manual] 
zaptn  nthorder zaveraged perturbation theory (ZAPT) [manual] 
omp2  orbitaloptimized secondorder MP perturbation theory [manual] 
omp3  orbitaloptimized thirdorder MP perturbation theory [manual] 
omp2.5  orbitaloptimized MP2.5 [manual] 
ocepa  orbitaloptimized coupled electron pair approximation [manual] 
cepa0  coupled electron pair approximation, equiv. linear. CCD [manual] 
cepa(0)  coupled electron pair approximation variant 0 [manual] 
cepa(1)  coupled electron pair approximation variant 1 [manual] 
cepa(3)  coupled electron pair approximation variant 3 [manual] 
acpf  averaged coupledpair functional [manual] 
aqcc  averaged quadratic coupled cluster [manual] 
qcisd  quadratic CI singles doubles (QCISD) [manual] 
cc2  approximate coupled cluster singles and doubles (CC2) [manual] 
ccsd  coupled cluster singles and doubles (CCSD) [manual] 
bccd  Brueckner coupled cluster doubles (BCCD) [manual] 
qcisd(t)  QCISD with perturbative triples [manual] 
ccsd(t)  CCSD with perturbative triples (CCSD(T)) [manual] 
fnodfccsd(t)  CCSD(T) with density fitting and frozen natural orbitals [manual] 
bccd(t)  BCCD with perturbative triples [manual] 
cc3  approximate CC singles, doubles, and triples (CC3) [manual] 
ccenergy  expert full control over ccenergy module 
cisd  configuration interaction (CI) singles and doubles (CISD) [manual] 
cisdt  CI singles, doubles, and triples (CISDT) [manual] 
cisdtq  CI singles, doubles, triples, and quadruples (CISDTQ) [manual] 
cin  nthorder CI [manual] 
fci  full configuration interaction (FCI) [manual] 
detci  expert full control over detci module 
gaussian2 (g2)  gaussian2 composite method [manual] 
sapt0  0thorder symmetry adapted perturbation theory (SAPT) [manual] 
sapt2  2ndorder SAPT, traditional definition [manual] 
sapt2+  SAPT including all 2ndorder terms [manual] 
sapt2+(3)  SAPT including perturbative triples [manual] 
sapt2+3  SAPT including all 3rdorder terms [manual] 
sapt2+(ccd)  SAPT2+ with CCbased dispersion [manual] 
sapt2+(3)(ccd)  SAPT2+(3) with CCbased dispersion [manual] 
sapt2+3(ccd)  SAPT2+3 with CCbased dispersion [manual] 
sapt0ct  0thorder SAPT plus charge transfer (CT) calculation [manual] 
sapt2ct  SAPT2 plus CT [manual] 
sapt2+ct  SAPT2+ plus CT [manual] 
sapt2+(3)ct  SAPT2+(3) plus CT [manual] 
sapt2+3ct  SAPT2+3 plus CT [manual] 
sapt2+(ccd)ct  SAPT2+(CCD) plus CT [manual] 
sapt2+(3)(ccd)ct  SAPT2+(3)(CCD) plus CT [manual] 
sapt2+3(ccd)ct  SAPT2+3(CCD) plus CT [manual] 
adc  2ndorder algebraic diagrammatic construction (ADC) [manual] 
eomcc2  EOMCC2 [manual] 
eomccsd  equation of motion (EOM) CCSD [manual] 
eomcc3  EOMCC3 [manual] 
name  calls method (aliases to name = ‘scf’) 

hf  HF 
rhf  HF with restricted reference 
uhf  HF with unrestricted reference 
rohf  HF with restricted openshell reference 
rscf  HF or DFT with restricted reference 
uscf  HF or DFT with unrestricted reference 
roscf  HF or DFT with restricted openshell reference 
name  calls method DFT [manual] 

b2plyp  B2PLYP Double Hybrid ExchangeCorrelation Functional 
b2plypd  B2PLYP Double Hybrid ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
b2plypd3  B2PLYP Double Hybrid ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
b2plypd3bj  B2PLYP Double Hybrid ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
b3lyp  B3LYP HybridGGA ExchangeCorrelation Functional 
b3lypchg  B3LYP HybridGGA ExchangeCorrelation Functional w/ Chai and HeadGordon Dispersion Correction 
b3lypd  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
b3lypd1  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D1 Dispersion Correction 
b3lypd3  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
b3lypd3bj  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
b3_x  Becke88 GGA Exchange (B3LYP weighting) 
b88_x  Becke88 GGA Exchange 
b970  B970 HybridGGA ExchangeCorrelation Functional 
b971  B971 HybridGGA ExchangeCorrelation Functional 
b972  B972 HybridGGA ExchangeCorrelation Functional 
b97d  B97D PureGGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
b97d3  B97D PureGGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
b97d3bj  B97D PureGGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
blyp  BLYP GGA ExchangeCorrelation Functional 
blypd  BLYP GGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
blypd1  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D1 Dispersion Correction 
blypd3  BLYP GGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
blypd3bj  BLYP GGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
bp86  BP86 GGA ExchangeCorrelation Functional 
bp86d  BP86 GGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
bp86d1  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D1 Dispersion Correction 
bp86d3  BP86 GGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
bp86d3bj  BP86 GGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
dsdblyp  DSDBLYP Dispersioncorrected SCS Double Hybrid XC Functional w/ Grimme’s D2 Dispersion Correction 
dsdpbep86  DSDPBEP86 Dispersioncorrected SCS Double Hybrid XC Functional (opt. for D2) w/ Grimme’s D2 Dispersion Correction 
dsdpbepbe  DSDPBEPBE Dispersioncorrected SCS Double Hybrid XC Functional w/ Grimme’s D2 Dispersion Correction 
ft97  FT97 GGA ExchangeCorrelation Functional 
ft97b_x  Filitov and Theil 1997 Exchange 
ft97_c  FT97 Correlation (Involves Ei functions) 
hcth  HCTH PureGGA ExchangeCorrelation Functional 
hcth120  HCTH120 PureGGA ExchangeCorrelation Functional 
hcth120d3  HCTH120 PureGGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
hcth120d3bj  HCTH120 PureGGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
hcth147  HCTH147 PureGGA ExchangeCorrelation Functional 
hcth407  HCTH407 PureGGA ExchangeCorrelation Functional 
hf+d  w/ Podeszwa and Szalewicz Dispersion Correction 
lyp_c  LYP Correlation 
m05  Heavily Parameterized Hybrid MetaGGA XC Functional 
m052x  Heavily Parameterized Hybrid MetaGGA XC Functional 
m052xd3  Heavily Parameterized Hybrid MetaGGA XC Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
m05d3  Heavily Parameterized Hybrid MetaGGA XC Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
p86_c  P86 Correlation (PZ81 LSDA + P86 GGA) 
pbe  PBE GGA ExchangeCorrelation Functional 
pbed  PBE GGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
pbed1  PBE GGA ExchangeCorrelation Functional w/ Grimme’s D1 Dispersion Correction 
pbed3  PBE GGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
pbed3bj  PBE GGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
pbe0  PBE0 Hybrid GGA ExchangeCorrelation Functional 
pbe02  PBE02 Double Hydrid ExchangeCorrelation Functional 
pbe0d  PBE0 Hybrid GGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
pbe0d3  PBE0 Hybrid GGA ExchangeCorrelation Functional w/ Grimme’s D3 (zerodamping) Dispersion Correction 
pbe0d3bj  PBE0 Hybrid GGA ExchangeCorrelation Functional w/ Grimme’s D3 (BJdamping) Dispersion Correction 
pbesol_x  PBEsol GGA Exchange Hole (Parameter Free) 
pbe_c  PBE Correlation 
pbe_x  PBE GGA Exchange Hole (Parameter Free) 
pw91  PW91 GGA ExchangeCorrelation Functional 
pw91_c  PW91 Correlation 
pw91_x  PW91 Parameterized GGA Exchange 
pw92_c  
pz81_c  PZ81 Correlation 
rpbe_x  RPBE GGA Exchange Hole (Parameter Free) 
sogga  Second Order GGA ExchangeCorrelation 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 MetaGGA XC Functional 
dldf+d  Dispersionless Hybrid MetaGGA XC Functional w/ Podeszwa and Szalewicz Dispersion Correction 
dldf+d09  Dispersionless Hybrid MetaGGA XC Functional w/ Podeszwa and Szalewicz Dispersion Correction 
wb88_x  B88 ShortRange GGA Exchange (HJS Model) 
wb97  Parameterized LRC B97 GGA XC Functional 
wb97x  Parameterized Hybrid LRC B97 GGA XC Functional 
wb97x2(lp)  Double Hybrid LRC B97 GGA XC Functional (Large Pople parametrization) 
wb97x2(tqz)  Double Hybrid LRC B97 GGA XC Functional (TQZ parametrization) 
wb97xd  Parameterized Hybrid LRC B97 GGA XC Functional with Dispersion w/ Chai and HeadGordon Dispersion Correction 
wblyp  BLYP SRXC Functional (HJS Model) 
wpbe  PBE SRXC Functional (HJS Model) 
wpbe0  PBE0 SRXC Functional (HJS Model) 
wpbe_x  PBE ShortRange GGA Exchange (HJS Model) 
wpbesol  PBEsol SRXC Functional (HJS Model) 
wpbesol0  PBEsol0 SRXC Functional (HJS Model) 
wpbesol_x  PBEsol ShortRange GGA Exchange (HJS Model) 
wsvwn  LSDA SRXC Functional 
ws_x  Slater ShortRange 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  
mrccsdt1a  CC through doubles with iterative triples (cheapest terms) 
mrccsdtq1a  CC through triples with iterative quadruples (cheapest terms) 
mrccsdtqp1a  CC through quadruples with iterative quintuples (cheapest terms) 
mrccsdtqph1a  CC through quintuples with iterative sextuples (cheapest terms) 
mrccsdt1b  CC through doubles with iterative triples (cheaper terms) 
mrccsdtq1b  CC through triples with iterative quadruples (cheaper terms) 
mrccsdtqp1b  CC through quadruples with iterative quintuples (cheaper terms) 
mrccsdtqph1b  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 
mrccsdt3  CC through doubles with iterative triples (all but the most expensive terms) 
mrccsdtq3  CC through triples with iterative quadruples (all but the most expensive terms) 
mrccsdtqp3  CC through quadruples with iterative quintuples (all but the most expensive terms) 
mrccsdtqph3  CC through quintuples with iterative sextuples (all but the most expensive terms) 
Parameters: 


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] 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('mp4')
>>> # [4] Converge scf as singlet, then run detci as triplet upon singlet reference
>>> molecule H2 {\\n0 1\\nH\\nH 1 0.74\\n}
>>> energy('scf')
>>> H2.set_multiplicity(3)
>>> energy('detci', bypass_scf=True)