Diabatic Valence-Hole Concept

A global diabatization scheme, based on the “valence-hole” concept, has been previously applied to model webs of avoided crossings that exist in four electronic-state symmetry manifolds of C2 (1Πg, 3Πg, 1Σu+, and 3Σu+). Here, this model is extended to the electronically excited states of four more molecules: CN (2Σ+), N2 (3Πu), SiC (3Π), and Si2 (3Πg). Many strangenesses in the spectroscopic observations (e.g., energy level structure, predissociation linewidths, and radiative lifetimes) for all four electronic state systems discussed here are accounted for by this unified model. The key concept of the model is valence-hole electron configurations: 3σ24σ11π45σ2 in CN (2Σ+), 2σg22σu11πu43σg21πg1 in N2 (3Πu), 5σ26σ17σ22π3 in SiC (3Π), and 4σg24σu15σg22πu3 in Si2 (3Πg), all of which have a triply occupied “valence-core” (i.e., 2σg22σu1 or the equivalent). These valence-hole configurations have a nominal bond order of three or higher and correlate with high-energy separated-atom limits with an np ← ns (n = 2, 3) promotion in one of the atomic constituents. On its way to dissociation, the strongly bound diabatic valence-hole state crosses multiple weakly bound or repulsive states, which belong to electron configurations with a completely filled valence-core. These curve crossings between diabatic potentials result in a network of many avoided crossings among multiple electronic states, analogous to the well-studied electronic structure landscape of ionic-covalent crossings in strongly ionic molecules. Considering the unique role of valence-hole states in shaping the global electronic structure, the valence-hole concept should be added to our intuitive framework of chemical bonding

Diabatic Valence-Hole Concept

A global diabatization scheme, based on the “valence-hole” concept, has been previously applied to model webs of avoided crossings that exist in four electronic-state symmetry manifolds of C2 (1Πg, 3Πg, 1Σu+, and 3Σu+). Here, this model is extended to the electronically excited states of four more molecules: CN (2Σ+), N2 (3Πu), SiC (3Π), and Si2 (3Πg). Many strangenesses in the spectroscopic observations (e.g., energy level structure, predissociation linewidths, and radiative lifetimes) for all four electronic state systems discussed here are accounted for by this unified model. The key concept of the model is valence-hole electron configurations: 3σ24σ11π45σ2 in CN (2Σ+), 2σg22σu11πu43σg21πg1 in N2 (3Πu), 5σ26σ17σ22π3 in SiC (3Π), and 4σg24σu15σg22πu3 in Si2 (3Πg), all of which have a triply occupied “valence-core” (i.e., 2σg22σu1 or the equivalent). These valence-hole configurations have a nominal bond order of three or higher and correlate with high-energy separated-atom limits with an np ← ns (n = 2, 3) promotion in one of the atomic constituents. On its way to dissociation, the strongly bound diabatic valence-hole state crosses multiple weakly bound or repulsive states, which belong to electron configurations with a completely filled valence-core. These curve crossings between diabatic potentials result in a network of many avoided crossings among multiple electronic states, analogous to the well-studied electronic structure landscape of ionic-covalent crossings in strongly ionic molecules. Considering the unique role of valence-hole states in shaping the global electronic structure, the valence-hole concept should be added to our intuitive framework of chemical bonding

New Insight into CO Formation during HCOOH Oxidation on Pt(111): Intermolecular Dehydration of HCOOH Dimers

Density functional theory simulations were performed to investigate CO formation during HCOOH oxidation on the Pt(111) surface in aqueous phase, through the intermolecular dehydrations of various HCOOH dimer models. The formation of CO that is found to poison Pt catalysts proceeds via four major intermolecular dehydration pathways as determined by varying initial HCOOH dimer structures. The computed rate-determining energy barriers of those four pathways are low, suggesting the kinetically and thermodynamically facile formation of intermediates and CO. This work demonstrates that the presence of HCOOH dimers accounts for the easy CO poisoning of Pt-based catalysts, and clarifies the controversy on the intermediates and mechanisms of CO formation found in different HCOOH oxidation experiments

Image_1_Midfrontal Theta and Posterior Parietal Alpha Band Oscillations Support Conflict Resolution in a Masked Affective Priming Task.TIF

<p>Past attempts to characterize the neural mechanisms of affective priming have conceptualized it in terms of classic cognitive conflict, but have not examined the neural oscillatory mechanisms of subliminal affective priming. Using behavioral and electroencephalogram (EEG) time frequency (TF) analysis, the current study examines the oscillatory dynamics of unconsciously triggered conflict in an emotional facial expressions version of the masked affective priming task. The results demonstrate that the power dynamics of conflict are characterized by increased midfrontal theta activity and suppressed parieto-occipital alpha activity. Across-subject and within-trial correlation analyses further confirmed this pattern. Phase synchrony and Granger causality analyses (GCAs) revealed that the fronto-parietal network was involved in unconscious conflict detection and resolution. Our findings support a response conflict account of affective priming, and reveal the role of the fronto-parietal network in unconscious conflict control.</p

The static dipole (α₁) and quadrupole (α₂) polarizabilities (in au) for the ground states of the alkali and alkaline-earth atoms

<p><b>Table 1.</b> The static dipole (α₁) and quadrupole (α₂) polarizabilities (in au) for the ground states of the alkali and alkaline-earth atoms. A recent review summarizes static dipole polarizabilities calculations and experiments [<a href="http://iopscience.iop.org/0953-4075/46/12/125004/article#jpb465825bib42" target="_blank">42</a>].</p> <p><strong>Abstract</strong></p> <p>Dispersion coefficients between the alkali metal atoms (Li–Rb) and alkaline-earth metal atoms (Be–Sr) are evaluated using matrix elements computed from frozen core configuration interaction calculations. Besides dispersion coefficients with both atoms in their respective ground states, dispersion coefficients are also given for the case where one atom is in its ground state and the other atom is in a low-lying excited state.</p

The dispersion coefficients (in au) for the ground state of alkali atoms interacting with the <em>n</em>s<em>n</em>p ¹P^<em>o</em> and ³P^<em>o</em> excited states of alkaline-earth atoms

<p><b>Table 3.</b> The dispersion coefficients (in au) for the ground state of alkali atoms interacting with the <em>n</em>s<em>n</em>p ¹P^<em>o</em> and ³P^<em>o</em> excited states of alkaline-earth atoms. <em>n</em> = 2, 3, 4 and 5 for Be, Mg, Ca and Sr, respectively. The notation <em>a</em>[<em>b</em>] means <em>a</em> <b>×</b> 10^<em>b</em>. Dispersion coefficients which could be influenced by an accidental degeneracy with pseudo-states in the alkali atom continuum are indicated by underlining.</p> <p><strong>Abstract</strong></p> <p>Dispersion coefficients between the alkali metal atoms (Li–Rb) and alkaline-earth metal atoms (Be–Sr) are evaluated using matrix elements computed from frozen core configuration interaction calculations. Besides dispersion coefficients with both atoms in their respective ground states, dispersion coefficients are also given for the case where one atom is in its ground state and the other atom is in a low-lying excited state.</p

The dispersion coefficients (in au) for the excited states of alkali atoms interacting with the ground states of alkaline-earth

<p><b>Table 5.</b> The dispersion coefficients (in au) for the excited states of alkali atoms interacting with the ground states of alkaline-earth. The notation <em>a</em>[<em>b</em>] means <em>a</em> <b>×</b> 10^<em>b</em>.</p> <p><strong>Abstract</strong></p> <p>Dispersion coefficients between the alkali metal atoms (Li–Rb) and alkaline-earth metal atoms (Be–Sr) are evaluated using matrix elements computed from frozen core configuration interaction calculations. Besides dispersion coefficients with both atoms in their respective ground states, dispersion coefficients are also given for the case where one atom is in its ground state and the other atom is in a low-lying excited state.</p

Tuning Light Absorption in Platinum(II) Terpyridyl π‑Conjugated Complexes: A First-Principle Study

Platinum­(II) terpyridyl complexes with a donor–acceptor (D–A) framework have long been considered as a promising component of dye-sensitized solar cells (DSSCs). To revealing the structure–property relationship of these highly modular systems, we have conducted a first-principle study at the time-dependent density functional theory (TDDFT) level on the [Pt­(^tBu₃tpy)­(−CC–Ph)_<i>n</i>]⁺ (^tBu₃tpy is 4,4′,4″-tri-<i>tert</i>-butyl-2,2′:6′,2″-terpyridine) complexes. It was found that their visible absorbance could be improved by elongating the donor chain with <i>n</i> (−CC–Ph) units, reaching a maximum at <i>n</i> = 16. It is noteworthy that such a simple concatenating protocol enables a remarkable charge transfer distance as long as 5 nm, implying a promising solution for the bottleneck problem of low charge separation rate in DSSCs. Furthermore, using a A–D–A system (two Pt­(^tBu₃tpy) acceptors bridged by one donor) effectively doubles the visible-harvesting ability, and twisting an benzene ring in the chain of donors to break π-conjugations can tune down light absorption in a quantitatively angular dependent manner. Finally, replacing the CC bond linker with CC double bond in donor leads to comparable light absorption ability while bestowing structural flexibility. These structure–property relationships thus provide efficient knobs for molecular rational design toward high performance dye-sensitized solar cells

Rhodium-Catalyzed Asymmetric Hydrogenation of β‑Acetylamino Acrylosulfones: A Practical Approach to Chiral β‑Amido Sulfones

The efficient and highly enantioselective catalytic asymmetric hydrogenation of β-acetylamino acrylosulfone has been achieved by employing Rhodium-TangPhos as catalyst. A series of β-amido sulfone products are obtained with excellent yields and good enantioselectivities

The dispersion coefficients (in au) for the lowest <em>n</em>d states of alkali atoms interacting with the ground states of the alkaline-earth atoms

<p><b>Table 6.</b> The dispersion coefficients (in au) for the lowest <em>n</em>d states of alkali atoms interacting with the ground states of the alkaline-earth atoms. The numbers in the square brackets denote powers of 10.</p> <p><strong>Abstract</strong></p> <p>Dispersion coefficients between the alkali metal atoms (Li–Rb) and alkaline-earth metal atoms (Be–Sr) are evaluated using matrix elements computed from frozen core configuration interaction calculations. Besides dispersion coefficients with both atoms in their respective ground states, dispersion coefficients are also given for the case where one atom is in its ground state and the other atom is in a low-lying excited state.</p