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 coupledcluster perturbative triples correction [H].

A(T) CORRECTION ENERGY
¶ The coupledcluster asymmetric perturbative triples correction [H].

MP4(T) CORRECTION ENERGY
¶ The MP4 triples component [H]. Quantity is second righthand term in Eq. (2).

AAA (T) CORRECTION ENERGY
¶ 
AAB (T) CORRECTION ENERGY
¶ 
ABB (T) CORRECTION ENERGY
¶ 
BBB (T) CORRECTION ENERGY
¶ Spin components of the UHFbased coupledcluster perturbative triples correction [H].

ACPF DIPOLE X
¶ 
ACPF DIPOLE Y
¶ 
ACPF DIPOLE Z
¶ The three components of the dipole [Debye] for the averaged coupledpair 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 coupledpair functional level of theory.

ACPF TOTAL ENERGY
¶ 
ACPF CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the averaged coupledpair functional level of theory.

AQCC DIPOLE X
¶ 
AQCC DIPOLE Y
¶ 
AQCC DIPOLE Z
¶ The three components of the dipole [Debye] for the averaged quadratic coupledcluster 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 coupledcluster level of theory.

AQCC TOTAL ENERGY
¶ 
AQCC CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the averaged quadratic coupledcluster 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 DIPOLE X
¶ 
CC ROOT n DIPOLE Y
¶ 
CC ROOT n DIPOLE Z
¶ The three components of the dipole [Debye] for the requested coupled cluster level of theory and root n (number starts at GS = 0).

CC ROOT n QUADRUPOLE XX
¶ 
CC ROOT n QUADRUPOLE XY
¶ 
CC ROOT n QUADRUPOLE XZ
¶ 
CC ROOT n QUADRUPOLE YY
¶ 
CC ROOT n QUADRUPOLE YZ
¶ 
CC ROOT n QUADRUPOLE ZZ
¶ The six components of the quadrupole [Debye Ang] for the requested coupled cluster level of theory and root n (numbering starts at GS = 0).

CC ROOT n TOTAL ENERGY
¶ 
CC ROOT n CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the requested coupled cluster level of theory and root n (numbering starts at GS = 0).

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 coupledcluster (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 coupledcluster (CCSD, CCSDT, up to CCn) level of theory.

CCSD(T) TOTAL ENERGY
¶ 
CCSD(T) CORRELATION ENERGY
¶ 
ACCSD(T) TOTAL ENERGY
¶ 
ACCSD(T) CORRELATION ENERGY
¶ 
CCSDT(Q) TOTAL ENERGY
¶ 
CCSDT(Q) CORRELATION ENERGY
¶ 
CC(n1)(n) TOTAL ENERGY
¶ 
CC(n1)(n) CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the perturbatively corrected coupledcluster (CCSD(T), aCCSD(T), CCSDT(Q), up to CC(n1)(n) level of theory.

CCSDT1a TOTAL ENERGY
¶ 
CCSDT1a CORRELATION ENERGY
¶ 
CCSDTQ1a TOTAL ENERGY
¶ 
CCSDTQ1a CORRELATION ENERGY
¶ 
CCn1a TOTAL ENERGY
¶ 
CCn1a CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the approximate coupledcluster (CCSD(T)1a, CCSDT(Q)1a, up to CCn1a) level of theory.

CCSDT1b TOTAL ENERGY
¶ 
CCSDT1b CORRELATION ENERGY
¶ 
CCSDTQ1b TOTAL ENERGY
¶ 
CCSDTQ1b CORRELATION ENERGY
¶ 
CCn1b TOTAL ENERGY
¶ 
CCn1b CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the approximate coupledcluster (CCSD(T)1b, CCSDT(Q)1b, up to CCn1b) level of theory.

CCSDT3 TOTAL ENERGY
¶ 
CCSDT3 CORRELATION ENERGY
¶ 
CCSDTQ3 TOTAL ENERGY
¶ 
CCSDTQ3 CORRELATION ENERGY
¶ 
CCn3 TOTAL ENERGY
¶ 
CCn3 CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the approximate coupledcluster (CCSD(T)3, CCSDT(Q)3, up to CCn3) level of theory.

CCSD(T)_L TOTAL ENERGY
¶ 
CCSD(T)_L CORRELATION ENERGY
¶ 
CCSDT(Q)_L TOTAL ENERGY
¶ 
CCSDT(Q)_L CORRELATION ENERGY
¶ 
CC(n1)(n)_L TOTAL ENERGY
¶ 
CC(n1)(n)_L CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the approximate coupledcluster (CCSD(T)_L, CCSDT(Q)_L, up to CC(n1)(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 nonzero 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 0).

CI STATEAVERAGED TOTAL ENERGY
¶ 
CI STATEAVERAGED CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for stateaveraged 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.

CPCORRECTED 2BODY INTERACTION ENERGY
¶ The interaction energy [H] considering only twobody interactions, computed with counterpoise correction. Related variable
UNCPCORRECTED 2BODY INTERACTION ENERGY
.\[E_{\text{IE}} = E_{dimer}  \sum_{monomer}^{n}{E_{monomer}^{\text{CP}}}\]

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.
\[\frac{1}{n}\sum_{rxn}^{n}{ \textsf{\textsl{name}}_{rxn}\text{REF}_{rxn}  }\]

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.
\[\frac{1}{n}\sum_{rxn}^{n}{\textsf{\textsl{name}}_{rxn}\text{REF}_{rxn}}\]

db_name DATABASE ROOTMEANSQUARE 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.
\[\sqrt{\frac{1}{n}\sum_{rxn}^{n}{(\textsf{\textsl{name}}_{rxn}\text{REF}_{rxn})^2}}\]

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 \(E_{\text{FCTL}}\) 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, \(E_{\text{DFT}}\) in Eq. (1).
\begin{align*} E_{\text{DFT}} & = E_{NN} + E_{1e^} + E_{2e^} + E_{xc} + E_{\text{D}} + E_{\text{DH}} \\ & = E_{\text{FCTL}} + E_{\text{D}} + E_{\text{DH}} \\ & = E_{\text{SCF}} + E_{\text{DH}} \end{align*}Unless the method is a DFT doublehybrid, this quantity is equal to
SCF TOTAL ENERGY
. If the method is neither a doublehybrid, nor dispersion corrected, this quantity is equal toDFT FUNCTIONAL TOTAL ENERGY
.

DFT XC ENERGY
¶ The functional energy contribution [H] to the total SCF energy (DFT only). Quantity \(E_{xc}\) in Eqs. (4) and (1).

DISPERSION CORRECTION ENERGY
¶ The dispersion correction [H] appended to an underlying functional when a DFTD method is requested. Quantity \(E_{\text{D}}\) in Eqs. (4) and (1).

DOUBLEHYBRID CORRECTION ENERGY
¶ The scaled MP2 correlation energy correction [H] appended to an underlying functional when a DHDFT method is requested. Quantity \(E_{\text{DH}}\) 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 \(E_{xc} = 0\)) terms in Eq. (4). Quantity \(E_{\text{HF}}\) 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 righthand 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 lefthand term in Eq. (2).(2)¶\[E_{\text{MP4}} = E_{\text{MP4(SDQ)}} + E_{\text{MP4(T)}}\]

MPn TOTAL ENERGY
¶ 
MPn CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the labeled Møller–Plesset perturbation theory level. n is MP perturbation order.

NUCLEAR REPULSION ENERGY
¶ The nuclear repulsion energy contribution [H] to the total SCF energy. Quantity \(E_{NN}\) in Eq. (4).
(3)¶\[E_{NN} = \sum_{i, j<i}^{N_{atom}}\frac{Z_i Z_j}{\mathbf{R}_i  \mathbf{R}_j}\]

OCEPA(0) TOTAL ENERGY
¶ 
OCEPA(0) CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the orbitaloptimized CEPA(0) level of theory.

OMP2 TOTAL ENERGY
¶ 
OMP2 CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the orbitaloptimized MP2 level of theory.

OMP3 TOTAL ENERGY
¶ 
OMP3 CORRELATION ENERGY
¶ The total electronic energy [H] and correlation energy component [H] for the orbitaloptimized MP3 level of theory.

ONEELECTRON ENERGY
¶ The oneelectron energy contribution [H] to the total SCF energy. Quantity \(E_{1e^}\) 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 TOTAL ENERGY
.

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

SAPT0 TOTAL ENERGY
¶ 
SSAPT0 TOTAL ENERGY
¶ 
SAPT2 TOTAL ENERGY
¶ 
SAPT2+ TOTAL ENERGY
¶ 
SAPT2+(3) TOTAL ENERGY
¶ 
SAPT2+3 TOTAL ENERGY
¶ The total electronic interaction energy [H] for the labeled SAPT level of theory.

SAPT2+(CCD) TOTAL ENERGY
¶ 
SAPT2+(3)(CCD) TOTAL ENERGY
¶ 
SAPT2+3(CCD) TOTAL ENERGY
¶ The total electronic interaction energy [H] for the labeled SAPT level of theory that incorporates coupledcluster dispersion.

SAPT2+DMP2 TOTAL ENERGY
¶ 
SAPT2+(3)DMP2 TOTAL ENERGY
¶ 
SAPT2+3DMP2 TOTAL ENERGY
¶ 
SAPT2+(CCD)DMP2 TOTAL ENERGY
¶ 
SAPT2+(3)(CCD)DMP2 TOTAL ENERGY
¶ 
SAPT2+3(CCD)DMP2 TOTAL ENERGY
¶ The total electronic interaction energy [H] for the labeled SAPT level of theory that incorporates MP2 induction correction.

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 correspondingTOTAL ENERGY
variables less this quantity. Constructed from Eq. (4), where this quantity is \(E_{\text{SCF}}\).\begin{align*} E_{\text{SCF}} & = E_{NN} + E_{1e^} + E_{2e^} + E_{xc} + E_{\text{D}} \\ & = E_{\text{FCTL/HF}} + E_{\text{D}} \end{align*}Unless the method includes a dispersion correction, this quantity is equal to
HF TOTAL ENERGY
(for HF) orDFT FUNCTIONAL TOTAL ENERGY
(for DFT). Unless the method is a DFT doublehybrid, this quantity is equal toDFT TOTAL ENERGY
.

TWOELECTRON ENERGY
¶ The twoelectron energy contribution [H] to the total SCF energy. Quantity \(E_{2e^}\) in Eq. (4).

UNCPCORRECTED 2BODY INTERACTION ENERGY
¶ The interaction energy [H] considering only twobody interactions, computed without counterpoise correction. Related variable
CPCORRECTED 2BODY INTERACTION ENERGY
.\[E_{\text{IE}} = E_{dimer}  \sum_{monomer}^{n}{E_{monomer}^{\text{unCP}}}\]