# PSI Variables by Alpha

Note

Lowercase letters in PSI variable names represent portions of the variable name that vary by root number, calculation order, etc. See text for fuller description.

`(T) CORRECTION ENERGY`

  The coupled-cluster perturbative triples correction [H].

`A-(T) CORRECTION ENERGY`

  The coupled-cluster asymmetric perturbative triples correction [H].

`MP4(T) CORRECTION ENERGY`

  The MP4 triples component [H]. Quantity is second right-hand term in Eq. (2).

`AAA (T) CORRECTION ENERGY`
`AAB (T) CORRECTION ENERGY`
`ABB (T) CORRECTION ENERGY`
`BBB (T) CORRECTION ENERGY`

  Spin components of the UHF-based coupled-cluster perturbative triples correction [H].

`ACPF DIPOLE X`
`ACPF DIPOLE Y`
`ACPF DIPOLE Z`

  The three components of the dipole [Debye] for the averaged coupled-pair functional level of theory.

`ACPF QUADRUPOLE XX`
`ACPF QUADRUPOLE XY`
`ACPF QUADRUPOLE XZ`
`ACPF QUADRUPOLE YY`
`ACPF QUADRUPOLE YZ`
`ACPF QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the averaged coupled-pair functional level of theory.

`ACPF TOTAL ENERGY`
`ACPF CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the averaged coupled-pair functional level of theory.

`AQCC DIPOLE X`
`AQCC DIPOLE Y`
`AQCC DIPOLE Z`

  The three components of the dipole [Debye] for the averaged quadratic coupled-cluster level of theory.

`AQCC QUADRUPOLE XX`
`AQCC QUADRUPOLE XY`
`AQCC QUADRUPOLE XZ`
`AQCC QUADRUPOLE YY`
`AQCC QUADRUPOLE YZ`
`AQCC QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the averaged quadratic coupled-cluster level of theory.

`AQCC TOTAL ENERGY`
`AQCC CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the averaged quadratic coupled-cluster level of theory.

`BRUECKNER CONVERGED`

  Value 1 (0) when the Brueckner orbitals have (have not) converged.

`CBS TOTAL ENERGY`
`CBS CORRELATION ENERGY`
`CBS REFERENCE ENERGY`

  The total electronic energy [H] and its breakdown into reference total energy [H] and correlation correction components [H] for the compound method requested through cbs().

`CC ROOT n TOTAL ENERGY`

  The total electronic energy [H] for the requested coupled cluster level of theory and root n (numbering starts at GS = 0).

`CC TOTAL ENERGY`
`CC CORRELATION ENERGY`

`CC2 TOTAL ENERGY`
`CC2 CORRELATION ENERGY`
`CC3 TOTAL ENERGY`
`CC3 CORRELATION ENERGY`
`CC4 TOTAL ENERGY`
`CC4 CORRELATION ENERGY`
`CCnn TOTAL ENERGY`
`CCnn CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the requested approximate coupled-cluster (CC2, CC3, up to CCnn) level of theory.

`CC DIPOLE X`
`CC DIPOLE Y`
`CC DIPOLE Z`

  The three components of the dipole [Debye] for the requested coupled cluster level of theory and root.

`CC QUADRUPOLE XX`
`CC QUADRUPOLE XY`
`CC QUADRUPOLE XZ`
`CC QUADRUPOLE YY`
`CC QUADRUPOLE YZ`
`CC QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the requested coupled cluster level of theory and root.

`CCSD TOTAL ENERGY`
`CCSD CORRELATION ENERGY`
`CCSDT TOTAL ENERGY`
`CCSDT CORRELATION ENERGY`
`CCSDTQ TOTAL ENERGY`
`CCSDTQ CORRELATION ENERGY`
`CCn TOTAL ENERGY`
`CCn CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the requested full coupled-cluster (CCSD, CCSDT, up to CCn) level of theory.

`CCSD(T) TOTAL ENERGY`
`CCSD(T) CORRELATION ENERGY`
`A-CCSD(T) TOTAL ENERGY`
`A-CCSD(T) CORRELATION ENERGY`
`CCSDT(Q) TOTAL ENERGY`
`CCSDT(Q) CORRELATION ENERGY`
`CC(n-1)(n) TOTAL ENERGY`
`CC(n-1)(n) CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the perturbatively corrected coupled-cluster (CCSD(T), a-CCSD(T), CCSDT(Q), up to CC(n-1)(n) level of theory.

`CCSDT-1a TOTAL ENERGY`
`CCSDT-1a CORRELATION ENERGY`
`CCSDTQ-1a TOTAL ENERGY`
`CCSDTQ-1a CORRELATION ENERGY`
`CCn-1a TOTAL ENERGY`
`CCn-1a CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the approximate coupled-cluster (CCSD(T)-1a, CCSDT(Q)-1a, up to CCn-1a) level of theory.

`CCSDT-1b TOTAL ENERGY`
`CCSDT-1b CORRELATION ENERGY`
`CCSDTQ-1b TOTAL ENERGY`
`CCSDTQ-1b CORRELATION ENERGY`
`CCn-1b TOTAL ENERGY`
`CCn-1b CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the approximate coupled-cluster (CCSD(T)-1b, CCSDT(Q)-1b, up to CCn-1b) level of theory.

`CCSDT-3 TOTAL ENERGY`
`CCSDT-3 CORRELATION ENERGY`
`CCSDTQ-3 TOTAL ENERGY`
`CCSDTQ-3 CORRELATION ENERGY`
`CCn-3 TOTAL ENERGY`
`CCn-3 CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the approximate coupled-cluster (CCSD(T)-3, CCSDT(Q)-3, up to CCn-3) level of theory.

`CCSD(T)_L TOTAL ENERGY`
`CCSD(T)_L CORRELATION ENERGY`
`CCSDT(Q)_L TOTAL ENERGY`
`CCSDT(Q)_L CORRELATION ENERGY`
`CC(n-1)(n)_L TOTAL ENERGY`
`CC(n-1)(n)_L CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the approximate coupled-cluster (CCSD(T)_L, CCSDT(Q)_L, up to CC(n-1)(n)L level of theory.

`CEPA(0) DIPOLE X`
`CEPA(0) DIPOLE Y`
`CEPA(0) DIPOLE Z`

  The three components of the dipole [Debye] for the coupled electron pair approximation variant 0 level of theory.

`CEPA(0) QUADRUPOLE XX`
`CEPA(0) QUADRUPOLE XY`
`CEPA(0) QUADRUPOLE XZ`
`CEPA(0) QUADRUPOLE YY`
`CEPA(0) QUADRUPOLE YZ`
`CEPA(0) QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the coupled electron pair approximation variant 0 level of theory.

`CEPA(0) TOTAL ENERGY`
`CEPA(0) CORRELATION ENERGY`
`CEPA(1) TOTAL ENERGY`
`CEPA(1) CORRELATION ENERGY`
`CEPA(2) TOTAL ENERGY`
`CEPA(2) CORRELATION ENERGY`
`CEPA(3) TOTAL ENERGY`
`CEPA(3) CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the requested variant of coupled electron pair approximation level of theory.

`CFOUR ERROR CODE`

  The non-zero return value from a Cfour execution.

`CI DIPOLE X`
`CI DIPOLE Y`
`CI DIPOLE Z`

  The three components of the dipole [Debye] for the requested configuration interaction level of theory and root.

`CI QUADRUPOLE XX`
`CI QUADRUPOLE XY`
`CI QUADRUPOLE XZ`
`CI QUADRUPOLE YY`
`CI QUADRUPOLE YZ`
`CI QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the requested configuration interaction level of theory and root.

`CI ROOT n -> ROOT m DIPOLE X`
`CI ROOT n -> ROOT m DIPOLE Y`
`CI ROOT n -> ROOT m DIPOLE Z`

  The three components of the transition dipole [Debye] between roots n and m for the requested configuration interaction level of theory.

`CI ROOT n -> ROOT m QUADRUPOLE XX`
`CI ROOT n -> ROOT m QUADRUPOLE XY`
`CI ROOT n -> ROOT m QUADRUPOLE XZ`
`CI ROOT n -> ROOT m QUADRUPOLE YY`
`CI ROOT n -> ROOT m QUADRUPOLE YZ`
`CI ROOT n -> ROOT m QUADRUPOLE ZZ`

  The three components of the transition quadrupole [Debye Ang] between roots n and m for the requested configuration interaction level of theory.

`CI ROOT n DIPOLE X`
`CI ROOT n DIPOLE Y`
`CI ROOT n DIPOLE Z`

  The three components of the dipole [Debye] for the requested configuration interaction level of theory and root n.

`CI ROOT n QUADRUPOLE XX`
`CI ROOT n QUADRUPOLE XY`
`CI ROOT n QUADRUPOLE XZ`
`CI ROOT n QUADRUPOLE YY`
`CI ROOT n QUADRUPOLE YZ`
`CI ROOT n QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the requested configuration interaction level of theory and root n.

`CI ROOT n TOTAL ENERGY`
`CI ROOT n CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the requested configuration interaction level of theory and root n (numbering starts at 1).

`CI STATE-AVERAGED TOTAL ENERGY`
`CI STATE-AVERAGED CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for state-averaged CI/CASSCF levels of theory.

`CI TOTAL ENERGY`
`CI CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the requested configuration interaction level of theory and root.

`CISD DIPOLE X`
`CISD DIPOLE Y`
`CISD DIPOLE Z`

  The three components of the dipole [Debye] for the configuration interaction singles and doubles level of theory and root.

`CISD QUADRUPOLE XX`
`CISD QUADRUPOLE XY`
`CISD QUADRUPOLE XZ`
`CISD QUADRUPOLE YY`
`CISD QUADRUPOLE YZ`
`CISD QUADRUPOLE ZZ`

  The six components of the quadrupole [Debye Ang] for the configuration interaction singles and doubles level of theory and root.

`CISD TOTAL ENERGY`
`CISD CORRELATION ENERGY`
`CISDT TOTAL ENERGY`
`CISDT CORRELATION ENERGY`
`CISDTQ CORRELATION ENERGY`
`CISDTQ TOTAL ENERGY`
`CIn CORRELATION ENERGY`
`CIn TOTAL ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the labeled configuration interaction level of theory and root. n is CI order for n > 4.

`CP-CORRECTED 2-BODY INTERACTION ENERGY`

  The interaction energy [H] considering only two-body interactions, computed with counterpoise correction. Related variable `UNCP-CORRECTED 2-BODY INTERACTION ENERGY`.

`CURRENT CORRELATION ENERGY`

  The correlation energy [H] corresponding to the `CURRENT ENERGY` variable.

`CURRENT ENERGY`

  The total electronic energy [H] of the most recent stage of a calculation (frequently overwritten). This is the quantity tracked by the geometry optimizer.

`CURRENT REFERENCE ENERGY`

  The total electronic energy [H] of the reference stage corresponding to the `CURRENT ENERGY` variable.

`db_name DATABASE MEAN ABSOLUTE DEVIATION`

  The mean absolute deviation [kcal mol-1] of the requested method name from the stored reference values for the requested reactions in database db_name. If no reference is available, this will be a large and nonsensical value.

`db_name DATABASE MEAN SIGNED DEVIATION`

  The mean deviation [kcal mol-1] of the requested method name from the stored reference values for the requested reactions in database db_name. If no reference is available, this will be a large and nonsensical value.

`db_name DATABASE ROOT-MEAN-SQUARE SIGNED DEVIATION`

  The rms deviation [kcal mol-1] of the requested method name from the stored reference values for the requested reactions in database db_name. If no reference is available, this will be a large and nonsensical value.

`DFT FUNCTIONAL TOTAL ENERGY`

  The total electronic energy [H] for the underlying functional of the requested DFT method, without any dispersion correction; the first four terms in Eq. (4) or (1). Quantity in Eqs. (4) and (1). Unless the method includes a dispersion correction, this quantity is equal to `SCF TOTAL ENERGY`.

`DFT TOTAL ENERGY`

  The total electronic energy [H] for the requested DFT method, in Eq. (1).

  (1)

  Unless the method is a DFT double-hybrid, this quantity is equal to `SCF TOTAL ENERGY`. If the method is neither a double-hybrid, nor dispersion corrected, this quantity is equal to `DFT FUNCTIONAL TOTAL ENERGY`.

`DFT XC ENERGY`

  The functional energy contribution [H] to the total SCF energy (DFT only). Quantity in Eqs. (4) and (1).

`DISPERSION CORRECTION ENERGY`

  The dispersion correction [H] appended to an underlying functional when a DFT-D method is requested. Quantity in Eqs. (4) and (1).

`DOUBLE-HYBRID CORRECTION ENERGY`

  The scaled MP2 correlation energy correction [H] appended to an underlying functional when a DH-DFT method is requested. Quantity in Eq. (1).

`FCI TOTAL ENERGY`
`FCI CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the full configuration interaction level of theory.

`HF TOTAL ENERGY`

  The total electronic energy [H] for the Hartree–Fock method, without any dispersion correction; the first three (or four, since ) terms in Eq. (4). Quantity in Eq. (4).

`LCC2 (+LMP2) TOTAL ENERGY`

  The total electronic energy [H] for the local CC2 level of theory.

`LCCSD (+LMP2) TOTAL ENERGY`

  The total electronic energy [H] for the local CCSD level of theory.

`MP2 TOTAL ENERGY`
`MP2 CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the MP2 level of theory.

`MP2.5 TOTAL ENERGY`
`MP2.5 CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the MP2.5 level of theory.

`MP3 TOTAL ENERGY`
`MP3 CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the MP3 level of theory.

`MP4(SDQ) TOTAL ENERGY`
`MP4(SDQ) CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the MP4 singles, doubles, quadruples level of theory. Quantity `MP4(SDQ) CORRELATION ENERGY` is first right-hand term in Eq. (2).

`MP4 TOTAL ENERGY`
`MP4 CORRELATION ENERGY`
`MP4(SDTQ) TOTAL ENERGY`
`MP4(SDTQ) CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the full MP4 level of theory. Quantity `MP4 CORRELATION ENERGY` / `MP4(SDTQ) CORRELATION ENERGY` is left-hand term in Eq. (2).

  (2)

`MPn TOTAL ENERGY`
`MPn CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the labeled Möller–Plesset perturbation theory level. n is MP perturbation order.

`NUCLEAR REPULSION ENERGY`

  The nuclear repulsion energy contribution [H] to the total SCF energy. Quantity in Eq. (4).

  (3)

`OCEPA(0) TOTAL ENERGY`
`OCEPA(0) CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the orbital-optimized CEPA(0) level of theory.

`OMP2 TOTAL ENERGY`
`OMP2 CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the orbital-optimized MP2 level of theory.

`OMP3 TOTAL ENERGY`
`OMP3 CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the orbital-optimized MP3 level of theory.

`ONE-ELECTRON ENERGY`

  The one-electron energy contribution [H] to the total SCF energy. Quantity in Eq. (4).

`QCISD TOTAL ENERGY`
`QCISD CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the quadratic configuration interaction singles and doubles level of theory.

`QCISD(T) TOTAL ENERGY`
`QCISD(T) CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the quadratic configuration interaction singles and doubles with perturbative triples correction level of theory.

`SAPT DISP ENERGY`
`SAPT ELST ENERGY`
`SAPT EXCH ENERGY`
`SAPT IND ENERGY`

  Respectively, the dispersion, electrostatics, exchange, and induction components of the total electronic interaction energy [H] for the the requested SAPT level of theory. The sum of these four components yields `SAPT ENERGY`.

`SAPT ENERGY`

  The total electronic interaction energy [H] for the requested SAPT level of theory.

`SAPT SAPT0 ENERGY`
`SAPT SAPT2 ENERGY`
`SAPT SAPT2+ ENERGY`
`SAPT SAPT2+(3) ENERGY`
`SAPT SAPT2+3 ENERGY`

  The total electronic interaction energy [H] for the labeled SAPT level of theory.

`SAPT SAPT2+(CCD) ENERGY`
`SAPT SAPT2+(3)(CCD) ENERGY`
`SAPT SAPT2+3(CCD) ENERGY`

  The total electronic interaction energy [H] for the labeled SAPT level of theory that incorporates coupled-cluster dispersion.

`SCF DIPOLE X`
`SCF DIPOLE Y`
`SCF DIPOLE Z`

  The three components of the SCF dipole [Debye].

`SCF QUADRUPOLE XX`
`SCF QUADRUPOLE XY`
`SCF QUADRUPOLE XZ`
`SCF QUADRUPOLE YY`
`SCF QUADRUPOLE YZ`
`SCF QUADRUPOLE ZZ`

  The six components of the SCF quadrupole [Debye Ang].

`SCF TOTAL ENERGY`

  The total electronic energy [H] of the SCF stage of the calculation. The `CORRELATION ENERGY` variables from subsequent stages of a calculation are often the corresponding `TOTAL ENERGY` variables less this quantity. Constructed from Eq. (4), where this quantity is .

  (4)

  Unless the method includes a dispersion correction, this quantity is equal to `HF TOTAL ENERGY` (for HF) or `DFT FUNCTIONAL TOTAL ENERGY` (for DFT). Unless the method is a DFT double-hybrid, this quantity is equal to `DFT TOTAL ENERGY`.

`TWO-ELECTRON ENERGY`

  The two-electron energy contribution [H] to the total SCF energy. Quantity in Eq. (4).

`UNCP-CORRECTED 2-BODY INTERACTION ENERGY`

  The interaction energy [H] considering only two-body interactions, computed without counterpoise correction. Related variable `CP-CORRECTED 2-BODY INTERACTION ENERGY`.

`ZAPTn TOTAL ENERGY`
`ZAPTn CORRELATION ENERGY`

  The total electronic energy [H] and correlation energy component [H] for the labeled Z-averaged perturbation theory level. n is ZAPT perturbation order.