Improved "Link-Free" Connectivity to Many New Host Programs
NBO 6 introduces a fundamentally new (link-free!) interactive connectivity
to electronic structure system (ESS) codes,
based on standard message-passing protocols made available as freeware to
all cooperating ESS vendors. Highly interactive ESS/NBO applications
that were previously restricted to Gaussian and GAMESS host programs
can now be carried out with a broad range of alternative ESS hosts.
Generalized Output and Labelling for Ground
and Excited Species
NBO 6 is now properly generalized and reformatted for arbitrary
electronic excitations and spin multiplicities, including the localized Lewis-like
and resonance patterns of excited states.
"Rydberg bond" and hybrids in 3T4 CH3CHO
Natural Cluster Unit (NCU) Analysis
NBO 6 now identifies the specific clustering patterns
(emergent "building blocks") that are associated
with specific ranges of interatomic interaction strength, allowing
one to isolate the distinguishing donor-acceptor interactions
over the entire range of metallic, molecular, and
supramolecular aggregation phenomena.
at τNCU = 0.350: (Li5)-0.447(Li+0.111)4
Natural Coulomb Electrostatics (NCE) Analysis
NBO 6 now provides
NPA-based evaluation of Lewis and non-Lewis contributions to apparent
Coulomb potential energy, providing an estimate
of classical-like "electrostatic" effects
to complement evaluation of steric
and resonance-type donor-acceptor contributions
to intra- and intermolecular interactions.
NCE atomic charges (L/NL) in (H2O)2
Natural Bond Critical Point (NBCP) Analysis
NBO 6 now provides comprehensive
NBO-based analysis of topological "bond critical point" (BCP)
properties, as characterized by the QTAIM theory of Bader
and coworkers. Atomic charges and other "basin" properties of
QTAIM-type "atoms in molecules" can thereby be quantitatively
compared and contrasted with corresponding properties of
NAO-based "natural atoms
in molecules" (NAIM), providing alternative
interpretations of many QTAIM-based topological descriptors.
QTAIM (dashed) vs. NAIM (solid) partitioning of CN
bond density in methylamine
Extended Multi-Center NBO Search
NBO 6 now conducts automated searches for both hypovalent 3c/2e
and hypervalent 3c/4e bond motifs (3CHB search), obviating the former need
for user intervention.
3c/2e sigma-bond in cyclobutenyl cation
Local NRT Analysis
NBO 6 now allows NRT analysis to be
restricted to local subregions (specified by input
bracket-list of "active" atoms), thereby allowing resonance features of much
larger polyaromatic and metallic systems to be analyzed
by "divide and conquer" strategy. Many other algorithmic improvements
make NRT searches more robust, reliable and efficient
than in previous versions.
Local and full NRT bond orders for
High-Order Multiple Bonding
NBO 6 now makes general provision for $CHOOSE
structures incorporating high-order metal-metal bond orders (up to
hextuple bonds!), consistent with
(and observed) bonding patterns
in dinuclear and polynuclear species.
"Beyond-σ" metal-metal bonds in HWWH
CML Support for NRT Resonance Structures
NBO 6 now includes "NRTCML" and other keywords
to generate Chemical Markup Language (.cml)
or other graphical-format input to display NRT resonance structures
in common structural viewers such as ChemDraw and MarvinView.
NRTCML diagrams for leading resonance structures of
General 1e Property (PROP)
NBO 6 now extends NBO analysis to any 1-electron property
for which matrix elements
are available from the host program. This allows
DIPOLE-style analysis to be extended
spin-density, kinetic energy, nuclear-electron
potential energy, and many other properties
of chemical interest.
Generalized operator and transformation
NBO 6 now provides enhanced (and simplified!) keyword tools to display
operator matrices for any available 1-e operator in any desired basis
or transformation matrices that explicitly relate any chosen pair of
basis sets to one another.
Complete Line of PC-Windows, MacOSX, and Linux/Unix Binary Options
for Interactive or Stand-Alone Usage
NBO 6 is now available in
fully functional binary .exe implementations
for PC-Windows XP/V/W7 or MacOSX10 systems, in addition
to common Linux/Unix configurations. For stand-alone GenNBO6 usage, just
include the "ARCHIVE" keyword in a standard NBO-linked electronic
structure job (including those from earlier NBO versions)
to obtain the .47 input file and run alternative analyses (without
recomputing the wavefunction) from the convenience of
the PC/Mac/Linux desktop. Alternatively, add binary NBO6
to the environment of your NBO6-compatible host ESS
and watch the ESS/NBO6 binary pair "come to life" to cooperatively
tackle complex interactive tasks that previously required linking.
With exceptions as noted above, NBO 6.0 is designed to be
compatible with earlier NBO 3/4/5-level versions as nearly as possible.
Experienced NBO users will find that familiar
options run practically unchanged, with smooth and intuitive
migration to newer keywords, features, and output format.