Character of Doped Holes in Nd1−xSrxNiO2

We investigate charge distribution in the recently discovered high-Tc superconductors, layered nickelates. With increasing value of charge-transfer energy, we observe the expected crossover from the cuprate to the local triplet regime upon hole doping. We find that the d−p Coulomb interaction Udp makes Zhang-Rice singlets less favorable, while the amplitude of local triplets at Ni ions is enhanced. By investigating the effective two-band model with orbitals of x2−y2 and s symmetries we show that antiferromagnetic interactions dominate for electron doping. The screened interactions for the s band suggest the importance of rare-earth atoms in superconducting nickelates.

Continuous color tuning of single-fluorophore emission via polymerization-mediated through-space charge transfer

Tuning emission color of molecular fluorophores is of fundamental interest as it directly reflects the manipulation of excited states at the quantum mechanical level. Despite recent progress in molecular design and engineering on single fluorophores, a systematic methodology to obtain multicolor emission in aggregated or solid states, which gives rise to practical implications, remains scarce. In this study, we present a general strategy to continuously tune the emission color of a single-fluorophore aggregate by polymerization-mediated through-space charge transfer (TSCT). Using a library of well-defined styrenic donor (D) polymers grown from an acceptor (A) fluorophore by controlled radical polymerization, we found that the solid-state emission color can be fine-tuned by varying three molecular parameters: (i) the monomer substituent, (ii) the end groups of the polymer, and (iii) the polymer chain length. Experimental and theoretical investigations reveal that the color tunability originates from the structurally dependent TSCT process that regulates charge transfer energy.

Electrostatics, Charge Transfer, and the Nature of the Halide-Water Hydrogen Bond

Binary halide–water complexes X^–(H₂O) are examined by means of symmetry-adapted perturbation theory, using charge-constrained promolecular reference densities to extract a meaningful charge-transfer component from the induction energy. As is known, the X^–(H₂O) potential energy surface (for X = F, Cl, Br, or I) is characterized by symmetric left and right hydrogen bonds separated by a <i>C_2v</i>-symmetric saddle point, with a tunneling barrier height that is < 2 kcal/mol except in the case of F^–(H₂O). Our analysis demonstrates that the charge-transfer energy is correspondingly small (< 2 kcal/mol except for X = F), considerably smaller than the electrostatic interaction energy. Nevertheless, charge transfer plays a crucial role determining the conformational preferences of X^–(H₂O) and provides a driving force for the formation of quasi-linear X^...H–O hydrogen bonds. Charge-transfer energies correlate well with measured O–H vibrational redshifts for both halide–water complexes as well as OH^–(H₂O) and NO₂^–(H₂O), providing some indication of a general mechanism. <br>

Electrostatics, Charge Transfer, and the Nature of the Halide-Water Hydrogen Bond

Binary halide–water complexes X^–(H₂O) are examined by means of symmetry-adapted perturbation theory, using charge-constrained promolecular reference densities to extract a meaningful charge-transfer component from the induction energy. As is known, the X^–(H₂O) potential energy surface (for X = F, Cl, Br, or I) is characterized by symmetric left and right hydrogen bonds separated by a <i>C_2v</i>-symmetric saddle point, with a tunneling barrier height that is < 2 kcal/mol except in the case of F^–(H₂O). Our analysis demonstrates that the charge-transfer energy is correspondingly small (< 2 kcal/mol except for X = F), considerably smaller than the electrostatic interaction energy. Nevertheless, charge transfer plays a crucial role determining the conformational preferences of X^–(H₂O) and provides a driving force for the formation of quasi-linear X^...H–O hydrogen bonds. Charge-transfer energies correlate well with measured O–H vibrational redshifts for both halide–water complexes as well as OH^–(H₂O) and NO₂^–(H₂O), providing some indication of a general mechanism. <br>

Ab Initio Effective One-Electron Potential Operators:Applications for Charge-Transfer Energy in Effective Fragment Potentials

The concept of effective one-electron potentials (EOP) has proven to be extremely useful in efficient description of electronic structure of chemical systems, especially extended molecular aggregates such as<br>interacting molecules in condensed phases. Here, a general method for EOP-based elimination of electron<br>repulsion integrals (ERIs) is presented, that is tuned towards the fragment-based calculation methodologies<br>such as the second generation of the effective fragment potentials (EFP2) method. Two general types of the<br>EOP operator matrix elements are distinguished and treated either via the distributed multipole expansion or<br>the extended density fitting schemes developed in this work. The EOP technique is then applied to reduce<br>the high computational costs of the effective fragment charge-transfer (CT) terms being the bottleneck of<br>EFP2 potentials. The alternative EOP-based CT energy model is proposed, derived within the framework of<br>intermolecular perturbation theory with Hartree–Fock non-interacting reference wavefunctions, compatible<br>with the original EFP2 formulation. It is found that the computational cost of the EFP2 total interaction<br>energy calculation can be reduced by up to 38 times when using the EOP-based formulation of CT energy,<br>as compared to the original EFP2 scheme, without compromising the accuracy for a wide range of weakly<br>interacting neutral and ionic molecular fragments. The proposed model can thus be used routinely within<br>the EFP2 framework.

Ab Initio Effective One-Electron Potential Operators:Applications for Charge-Transfer Energy in Effective Fragment Potentials

The concept of effective one-electron potentials (EOP) has proven to be extremely useful in efficient description of electronic structure of chemical systems, especially extended molecular aggregates such as<br>interacting molecules in condensed phases. Here, a general method for EOP-based elimination of electron<br>repulsion integrals (ERIs) is presented, that is tuned towards the fragment-based calculation methodologies<br>such as the second generation of the effective fragment potentials (EFP2) method. Two general types of the<br>EOP operator matrix elements are distinguished and treated either via the distributed multipole expansion or<br>the extended density fitting schemes developed in this work. The EOP technique is then applied to reduce<br>the high computational costs of the effective fragment charge-transfer (CT) terms being the bottleneck of<br>EFP2 potentials. The alternative EOP-based CT energy model is proposed, derived within the framework of<br>intermolecular perturbation theory with Hartree–Fock non-interacting reference wavefunctions, compatible<br>with the original EFP2 formulation. It is found that the computational cost of the EFP2 total interaction<br>energy calculation can be reduced by up to 38 times when using the EOP-based formulation of CT energy,<br>as compared to the original EFP2 scheme, without compromising the accuracy for a wide range of weakly<br>interacting neutral and ionic molecular fragments. The proposed model can thus be used routinely within<br>the EFP2 framework.