AIM 
Atoms In Molecules  method of topological analysis
of distribution of electron density. 
AM1 
Austin Model 1  semiempirical method
of quantum chemistry [DEWAR and
ZOEBISCH (1985)]. 
AO 
Atomic Orbital. 
AOM 
Angular Overlap Model. 
ASE 
Aromatic Stabilization Energy. 
BDE 
Bond Dissociation Energy. 
BEBO 
Bond Energy Bond Order method. 
B3LYP 
Becke Lee, Yang and Parr hybrid functional
which defines the exchange functional as a linear combination of
HF, local and and gradientcorrected exchange terms [BECKE
(1988), LEE (1988)]. 
BO 
Born  Oppenheimer approximation. 
BRE 
Bond Resonance Energy. 
BSSE 
Basis Set Superposition Error. 
CAS 
Complete Active Space. 
CASPT 
Complete Active Space Perturbation Theory. 
CASPT2 
CASPT based method with second order
perturbation theory [ANDERSON
(1992)]. 
CASSCF 
CompleteActiveSpace SCF method of
solution of the electronic Schrödingerequation [ROOS
(1980)]. 
CBS 
Complete Basis Set of orbitals. 
CC 
Coupled Cluster. 
CCSD(T) 
Coupled Cluster Single, Double (Triple) excitations. 
CDW 
Charge Density Waves. 
CEPA 
Coupled ElectronPair Approximation. 
CHF 
Coupled HF method. 
CI 
Configuration Interaction. 
3 x 3 CI 
CI for all three possible singlet configurations
in the twoelectron twoorbital model. 
CID 
CI, Double excitations only,
Collision Induced Dissociation. 
CIDNP 
Chemically Induced Dynamic Nuclear Polarization. 
CIS 
CI, Single excitations only. 
CISD 
Single and Double excitations, single reference
CI method. 
CISDT 
CISD plus Triple excitations. 
CISDQ (or QCISD) 
CISD plus Quadruple excitations, see also
QCISD. 
CISDTQ 
CISD plus triple and quadruple excitations. 
CMO 
Canonical Molecular Orbital. 
CNDO 
Complete Neglect of Differential Overlap. 
CNDO/2 
Complete Neglect of Differential Overlap, semiempirical
method of quantum chemistry with paramerization according to Pople
& Segal [POPLE and SEGAL
(1966)]. 
CNDO/S 
Complete Neglect of Differential Overlap/
Spectroscopic parametrization according to Del Bene &
Jaffe [DEL BENE (1968)]. 
COOP 
Crystal Orbital Overlap Population. 
CSD 
Cambridge Structural Database. 
CT 
Charge Transfer. 
DE 
Delocalization Energy. 
DFT 
Density Functional Theory. 
DIM 
Diatomics In Molecules. 
DNMR 
Dynamic NMR spectroscopy 
DOS 
Density of States. 
DRE 
Dewar Resonance Energy. 
DRP 
Dynamic Reaction Path. 
DZ 
DoubleZeta type of basis set. 
DZP 
DZ plus Polarization function basis set. 
EA 
Electron Affinity. 
EAN 
Effective Atomic Number rule. 
ECP 
Effective Core Potential. 
EFF 
Empirical Force Field. 
EHMO 
Extended Hückel Molecular Orbital, semiempirical
method of quantum chemistry [HOFFMANN
(1963)].

EHT 
Extended Hückel Theory. 
EM 
Effective Molarity. 
EPR 
Electron Paramagnetic Resonance. 
ESR 
Electron Spin Resonance spectroscopy. 
ET 
Electron Transfer. 
EXAFS 
Extended Xray Absorption Fine Structure spectroscopy
[BERTRAGNOLI (1994)] 
FSGO 
Floating Spherical Gaussian Orbitals. 
G1 
Gaussian1, a method for ab initio calculations
based on the MP4/6311G(d.p)/MP2/631G(d) scheme with corrections
of the incompletness of the basis through inclusion of
diffuse functions and extra d and f functions for nonhydrogen
atoms [POPLE, HEADGORDON, et. al.
(1989)]. 
G2 
Gaussian 2, a method for ab initio
calculations that improves the G1 methodology byincluding corrections
for the larger 6311+G(3df, 2p) basis set and providing empirical
correction for the number of valence electron pairs. The theory
corresponds effectively to calculations at the QCISD(T)/6311 +
G(3df, 2p) level with zeropoint vibrational energy (ZPE) and higher
level correlations [CURTISS, RAGHAVACHARI,
et. al. (1991)]. 
GIAO 
Gauge Invariant Atomic Orbitals. 
GTO 
Gaussian  Type Orbitals.

GVB 
Generalized Valence Bond method. 
GVBCI 
GVB plus CI method. 
HAM 
Hydrogenic Atoms in Molecules method. HAM/N (N=1,2,3)
 versions of the method [LINCHOLM
(1985)]. 
HE 
Half Electron method. 
HF 
HartreeFock method. 
HMO 
Hückel Molecular Orbital. 
HOMO 
Highest Occupied Molecular Orbital. 
HOMAS 
Harmonic Oscillator Model of Aromatic Stabilization. 
HOSE 
Harmonic Oscillator Stabilization Energy. 
HRE 
Hückel Resonance Energy. 
HSE 
Homodesmotic Stabilization Energy. 
HSRE 
HessSchaad Resonance Energy. 
ICCI 
Internally Contracted CI method. 
IEPA 
Independent ElectronPair Approximation. 
IGLO 
Individual Gauge for Localized Orbitals. 
IRC 
Intrinsic Reaction Coordinate. 
INDO 
Intermediate Neglect of Differential Overlap. A
semiempirical method of quantum chemistry [POPLE,
BEVERIDGE, and DOBOSH (1967)]. 
INDO/S 
Intermediate Neglect of Differential Overlap/ Spectroscopic
parametrization [ANDERSON, EDWARDS,
and ZERNER (1986)]. 
INDO/S  CI 
Intermediate Neglect of Differential Overlap/ Spectroscopic
parametrization accounting for Configuration Interaction
[FOX (1993)]. 
IP 
Ionization Potential. 
ISE 
Isodesmic Stabilization Energy. 
JT 
Jahn  Teller effect. 
KIE 
Kinetic Isotope Effect. 
LCAO MO 
Linear Combination of Atomic Orbitals representation
of Molecular Orbitals. 
LDA 
Local Density Approximatiom in DFT. 
LE 
Localization Energy. 
LFER 
Linear Free Energy Relationships. 
LFSE 
Linear Field Stabilization Energy. 
LMO 
Localized Molecular Orbital. 
LORG 
Localized Orbital, Localized Origin method. 
LUMO 
Lowest Unoccupied Molecular Orbital. 
MBPT(n) 
ManyBody Perturbation Theory of nth Order. 
MC 
Monte Carlo method. 
MC SCF 
MultiConfiguration SCF theory. 
MCIGLO 
MultiConfiguration IGLO. 
MCPF 
ModifiedCoupledPairFunctional. 
MD 
Molecular Dynamics method. 
MEP 
Molecular Electrostatic Potential. 
MERP 
Minimum Energy Reaction Path. 
MIDIN 
MIDdle size splitvalence type contracted
GTO basis set (N = 14). 
MINDO 
Modified INDO, MINDO/N (N = 1,2,3)  versions of
the semiempirical method of quantum chemistry [DEWAR,
BINGHAM, and LO (1975)]. 
MININ 
MINImaltype contracted GTO basis set (N
= 14). 
MM 
Molecular Mechanics. 
MM2 
Molecular Mechanics force field, 2d version of
the parametric set and the program using molecular mechanics
[ALLINGER (1977)]. 
MM3 
Molecular Mechanics force field, 3d version of
the parametric set and the computer program [ALLINGER,CHEN,
and RAHMAN (1993)]. 
MMX 
Molecular Mechanics empirical force field [GAJEWSKII
(1990)]. 
MNDO 
Modified Neglect of Diatomic Overlap. A semiempirical
method of quantum chemistry [DEWAR
and THIEL (1977)]. 
MNDOC 
MNDO method with a perturbative treatment of electron
Correlation [THIEL (1981)]. 
MO 
Molecular Orbital. 
MOVB 
MO VB theory. 
MPA 
Mulliken Population Analysis. 
MPN (N = 24) 
MØllerPlesset perturbation
theory of order N for electron correlation [MØLLER
(1934)]. 
MP2/631G*//HF/631G* 
Example of abridged notation to specify the type
of level used in a givencalculation : the MP2 theory and of the
631G* basis set, at the geometry optimized at HF/631G* method. 
MRD 
Multireference Double substitution, method of. 
MRDCI 
MRD with inclusion of CI. 
N31G, etc. 
Pople's basis set. Notations of this basis sets
like NijG or NijkG should be encoded as follows: N  number of
Gaussian primitives (GTOs) for the inner shells; ij or ijk  number
of Gaussian primitives for contractions in the valence shell. The
ij notations correspond to basis sets of valence DZ quality and
ijk notations indicate split valence sets of triple zeta (TZ) quality.
NijG* denotes a polarized basis set augmented with d type functions
on heavy atoms only ; NijG** (or NijG(d,p)  basis set with pfunctions
on hydrogen atoms. 
N31+G(d), etc^{#.} 
Pople's basis set with diffuse function.
For example, 6311+G(2df,2pd) putting 2d functions and 1f function
on heavy atoms (plus diffuse functions), and 2p functions and 1d
function on hydrogens.
#) According to the IUPAC recommendation, the actual construction
of the basis sets for each atom should be specified as (abc...,
ghi..., lm..., o...), where a is the number of primitives usually
GTOs) in the first contracted s function, b is the number of primitives
in the second contracted s function, etc., g is the number of primitives
in the first contracted p function , l is the number of primitives
in thecontracted d function, and o is the number of primitives in
the first contracted f function. Thus, a 631+G* basis for carbon
should be designated as (6311, 311, 1)
"Guidelines for the Presentation of Quantum Mechanical Computational
Data in Organic Chemistry".Prepared for publication by Albright
& Halevi [ALBRIGHT and HALEVI
(1992)]. 
NAO 
Natural Atomic Orbital. 
NBO 
Natural Bond Orbital. 
NDDO 
Neglect of Diatomic Differential Overlap. A semiempirical
method of quantum chemistry [POPLE,
SANTRY, and SEGAL (1965)]. 
NHO 
Natural Hybrid Orbital. 
NICS 
Nuclear Independent Chemical Shift. 
NMR 
Nuclear Magnetic Resonance. 
NPA 
Natural Population Analysis. 
OCAMS 
Orbital Correspondence Analysis in Maximum Symmetry. 
OFGF 
Outer Valence Green's Function method. 
PA 
Proton Affinity. 
PCILO 
Perturbative Configuration Interaction using Localized
Orbitals method. 
PCM 
Polarizable Continuum Model of solvation. 
PES 
Potential Energy Surface.
Photoelectron Spectroscopy.

PLM 
Principle of Least Motion. 
PM3 
Parametric Method 3  a semiempirical method of quantum
chemistry based on theMNDO scheme [STEWART
(1989)]. 
PMO 
Perturbation MO theory. 
PNO 
Pair Natural Orbitals 
POAV 
p  Orbital Axis Vector. 
PPFMO 
Polarized pFrontier MO
theory [HUANG (1993)]. 
PPP 
PariserParrPople, method of. 
PRDDO 
Partial Retention of Diatomic Differential Overlap.
A semiempirical method of quantum chemistry [HALGREN
(1973)]. 
PT 
Perturbation Theory. 
QCI 
Quadratic Configuration Interaction, method of. 
QCISD 
Quadratic CI with Single and Double
excitations, see also CISD. 
QCISD (T) 
QCISD with perturbational treatment of Triple excitations. 
QCISD (TQ) 
QCISD with perturbational treatment of Triple
and Quadruple excitations. 
QMRE 
Quantum Mechanical Resonance Energy. 
QSAR 
Quantitative Structure  Activity Relationships. 
RCI 
Ring Current Index. 
RE 
Resonance Energy. 
REPE 
Resonance Energy Per Electron. 
RHF 
Restricted HF theory. 
ROHF 
Restricted Open shell HF theory. 
RPH 
Reaction Path Hamiltonian. 
RRKM 
Rice  Ramsperger  Kassel  Marcus theory. 
SAM1 
SemiAbinitio Model 1. Version 1 of a semiempirical
method of quantum chemistry [DEWAR,
JIE, and YU (1993)]. 
SC 
SpinCoupled method. 
SCD 
State Correlation Diagram. 
SCF 
SelfConsistent Field, method of. 
SCIPCM 
SelfConsistent Isodensity Polarizable Continuum Model
of solvation. 
SCRF 
SelfConsistent Reaction Field, method of. 
SDW 
Spin Density Wave. 
SE 
Strain Energy. 
SET 
Single Electron Transfer. 
SINDO 
Symmetrically orthogonalized INDO method.
SINDO1  a version of the method [NANDA
(1980)]. 
SOJT 
SecondOrder Jahn  Teller effect. 
SO 
Spin  Orbital. 
SOMO 
Singly Occupied Molecular Orbital. 
STO 
Slater  Type Orbital [SLATER
(1930)]. 
STO  NG 
STO approximation by the sum of N (36) GTOs. 
TCSCF 
Two Configuration SCF method , a special case of
MC SCF. 
TRE 
Topological Resonance Energy. 
TS 
Transition State. 
TSS 
Transition State Spectroscopy 
UHF 
Unrestricted HF method. 
UMNDO 
UHF version of MNDO. 
VAT 
Vibration Assisted Tunnelling. 
VB 
Valence Bond theory 
VBCM 
Valence Bond Configuration Mixing model. 
VDW 
van der Waals interactions. 
VSEPR 
Valence Shell ElectronPair Repulsion method. 
VSIP 
Valence State Ionization Potential. 
XPS 
Xray Photoelectron Spectroscopy. 
ZDO 
Zero Differential Overlap. 
ZINDO 
Zerner’s INDO method. 
ZPE 
Zero Point vibration Energy. 
ZPVE 
Zero Point Vibration Energy. 