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) 
mp2  2ndorder MollerPlesset perturbation theory (MP2) 
dfmp2  MP2 with density fitting 
dcft  density cumulant functional theory 
mcscf  multiconfigurational self consistent field (SCF) 
sapt0  0thorder symmetry adapted perturbation theory (SAPT) 
sapt2  2ndorder SAPT, traditional definition 
sapt2+  SAPT including all 2ndorder terms 
sapt2+(3)  SAPT including perturbative triples 
sapt2+3  
sapt0ct  0thorder SAPT plus charge transfer (CT) calculation 
sapt2ct  SAPT2 plus CT 
sapt2+ct  SAPT2+ plus CT 
sapt2+(3)ct  SAPT2+(3) plus CT 
sapt2+3ct  SAPT2+3 plus CT 
cc2  approximate coupled cluster singles and doubles (CC2) 
ccsd  coupled cluster singles and doubles (CCSD) 
bccd  Brueckner coupled cluster doubles (BCCD) 
cc3  approximate coupled cluster singles, doubles, and triples (CC3) 
ccsd(t)  CCSD with perturbative triples 
bccd(t)  BCCD with perturbative triples 
ccenergy  expert full control over ccenergy module 
mpn  nthorder Moller–Plesset perturbation theory 
zaptn  nthorder zaveraged perturbation theory (ZAPT) 
cisd  configuration interaction (CI) singles and doubles (CISD) 
cisdt  CI singles, doubles, and triples (CISDT) 
cisdtq  CI singles, doubles, triples, and quadruples (CISDTQ) 
cin  nthorder CI 
fci  full configuration interaction (FCI) 
detci  expert full control over detci module 
adc  2ndorder algebraic diagrammatic construction (ADC) 
eomcc2  EOMCC2 
eomccsd  equation of motion (EOM) CCSD 
eomcc3  EOMCC3 
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 
dfscf  HF or DFT with density fitting 
name  calls method 

b3lyp  B3LYP HybridGGA ExchangeCorrelation Functional 
b3lypd  B3LYP HybridGGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
b3lyp5  B3LYP5 HybridGGA ExchangeCorrelation Functional 
b3lyp5d  B3LYP5 HybridGGA ExchangeCorrelation Functional w/ Grimme’s D2 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 
blyp  BLYP GGA ExchangeCorrelation Functional 
blypd  BLYP GGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
bp86  BP86 GGA ExchangeCorrelation Functional 
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 
hcth147  HCTH147 PureGGA ExchangeCorrelation Functional 
hcth407  HCTH407 PureGGA ExchangeCorrelation Functional 
lyp_c  LYP Correlation 
m05  Heavily Parameterized Hybrid MetaGGA XC Functional 
m052x  Heavily Parameterized Hybrid MetaGGA XC Functional 
p86_c  P86 Correlation (PZ81 LSDA + P86 GGA) 
pbe  PBE GGA ExchangeCorrelation Functional 
pbed  PBE GGA ExchangeCorrelation Functional w/ Grimme’s D2 Dispersion Correction 
pbe0  PBE0 Hybrid GGA ExchangeCorrelation Functional 
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 
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 
wb88_x  B88 ShortRange GGA Exchange (HJS Model) 
wb97  Parameterized LRC B97 GGA XC Functional 
wb97x  Parameterized Hybrid LRC B97 GGA XC Functional 
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 

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: 


Examples : 
>>> # [1] Coupledcluster singles and doubles calculation with psi code
>>> energy('ccsd')
>>> # [2] Chargetransfer SAPT calculation with scf projection from small into requested basis
>>> energy('sapt0ct',cast_up=True)
>>> # [3] Arbitraryorder MPn calculation
>>> energy('mp4')