We present domain-based local pair natural orbital Møller-Plesset second-order perturbation theory (DLPNO-MP2) with Born-von Kármán boundary (BvK) conditions. The approach is based on well-localized Wannier functions in an LCAO formalism and extends the molecular DLPNO-MP2 implementation in the Turbomole program package to periodic systems. The PNOs are formed through a projected atomic orbital (PAO)-orbital specific virtual (OSV)-PNO cascade, using BvK PAOs and OSVs as intermediaries in an analogous manner to the molecular scheme. Our chargeless and surface-dipole corrected local density fitting approach is shown to be numerically stable and to ensure convergent lattice summations over the periodic images for the two- and three-center Coulomb integrals. Through careful benchmarking, we show that the DLPNO approximations in the BvK-DLPNO-MP2 methods are entirely consistent with those of molecular DLPNO-MP2 calculations and with an alternative periodic approach, Megacell-DLPNO-MP2, reported in Paper II of this series [Zhu et al., J. Chem. Phys. 163 (2025)]. The method exhibits a smooth convergence to the canonical correlation energy upon tightening the PNO truncation threshold. Reference MP2 correlation energies are provided for a set of 2D and 3D periodic systems using a triple-zeta basis and supercell sizes up to 13 × 13 and 7 × 7 × 7, respectively.

We present a strategy combining machine learning and first-principle calculations to achieve highly accurate nuclear quadrupolar coupling constant predictions. Our approach employs two distinct machine-learning frameworks: a machine-learned force field to generate molecular dynamics trajectories and a second model for electric field gradients that preserves rotational and translational symmetries. By incorporating thermostat-driven molecular dynamics sampling, we enable the prediction of quadrupolar coupling constants in highly disordered materials at finite temperatures. We validate our method by predicting the tetragonal-to-cubic phase transition temperature of the organic-inorganic halide perovskite MAPbI3, obtaining results that closely match experimental data.

BiCuSeO oxychalcogenides are promising p-type thermoelectric (TE) materials, yet their TE efficiency is limited by an extremely low intrinsic carrier concentration of ∼ 1018cm-3. In this study, it is demonstrated that systematic Cd doping triggers the onset of TE performance of BiCuSeO. The substitution of Bi3+ with Cd2+ in a series of Bi1-xCdxCuSeO (x = 0, 0.02, 0.04, 0.06, and 0.08) polycrystalline alloys induces a predictable, near-linear increase in carrier concentration, reaching 3.19 × 1020cm-3 at x = 0.08 with doping efficiency between 0.27 and 0.41 per dopant. The influence was particularly dramatic at the initial doping (x = 0.02), which boosted the carrier concentration to 1.08 × 1020cm-3 from an extremely low carrier concentration of 2.82 × 1018 of the pristine sample. This substantial increase successfully activated a high effective mass and power factor. The Boltzmann transport calculations confirm that the electrical transport properties are radically optimized in this high carrier concentration regime. Lattice thermal conductivity decreased from 1.47 W/mK at x = 0 to 1.14 W/mK for x = 0.02 at 300K, with the reduction being more pronounced gradually at higher doping levels. Consequently, the thermoelectric figure of merit zT showed a significant improvement by 70%, reaching 0.29 for x = 0.02 at 650K. The optimal TE performance was reached for x ≥ 0.04, as zT values of 0.38-0.43 were attained, representing up to 150% enhancement over the pristine sample. This study demonstrated a facile doping strategy to activate the TE performance of compounds often dismissed for their low intrinsic carrier concentration.

Investigating water structures at aqueous interfaces has been a central focus in the field of nonlinear surface spectroscopy over decades. This large body of work leads to a conclusion that asymmetric OH stretches should be largely silent in sum frequency generation (SFG) spectra. Nonetheless, our recent studies show chiral-specific SFG response of water originating from the first hydration shell of proteins and DNA arising from a sum of equal-magnitude and opposite-phase symmetric and asymmetric OH stretches, resulting in an oppositely signed couplet. Motivated initially by this apparently inconsistent behavior for chiral-specific vs conventional (achiral) SFG, we demonstrate herein a fundamental argument for the appearance of the oppositely signed couplets in chiral-specific vibrational SFG. The interplay between two foundational optical relations, Kramers-Kronig relations and index-interchange symmetry arising in the adiabatic zero-frequency limit (often referred to as Kleinman symmetry), is shown to require the imaginary resonant contributions to the tensors describing chiral-specific SFG responses to collectively sum to zero. In brief, all indices within the surface susceptibility must become interchangeable in the degenerate, zero-frequency adiabatic limit. From Kramers-Kronig relations connecting the real and imaginary susceptibility, this asymptotic limit in the real susceptibility can only be met if the imaginary-valued resonant contributions over the relevant spectral range sum to zero. These symmetry constraints were found to agree with density functional theory calculations on small water clusters and with experimental and computational phase-resolved chiral-specific SFG spectra. These symmetry requirements provide constraints for analyzing phase-resolved chiral-specific SFG spectra for extracting structural information about chiral molecules at interfaces.

Crystallization pressure can cause significant damage to various materials, particularly cementitious materials and geomaterials. Understanding the mechanism behind this pressure is essential to preserve these materials and limit their degradation. Although the phenomenon has been known for a long time, the results from theoretical calculations and experimental observations remain very heterogeneous. The confined crystallization process relies on the presence of a nanometric wetting film at the interfaces to sustain crystal growth. The conditions for the existence and stability of these nanometric films, as well as their transport properties, remain largely unknown due to the great difficulty of studying them experimentally. In this paper, we determine by molecular simulation the limits of the crystallization pressure phenomenon at the finest scale. We perform hybrid configurational bias Monte Carlo-molecular dynamics simulations to determine the critical pressure at which the wetting film separating the crystal from the pore surface disappears under various temperature and pressure conditions. We illustrate the influence of the wetting film's composition on the crystallization process by comparing a confined pure water film to a confined brine solution film. The obtained results enable us to establish both an upper and a lower boundary for the crystallization pressure, to define the range of applicability for the existing theoretical equations, and to identify the limiting factors affecting the transport properties in the constrained films.

Two-dimensional electronic spectroscopy (2DES) provides a detailed picture of electronically nonadiabatic dynamics that can be interpreted with the aid of simulations. Here, we develop and contrast trajectory-based nonadiabatic dynamics approaches for simulating 2DES spectra. First, we argue that an improved pure-state Ehrenfest approach can be constructed by decomposing the initial coherence into a sum of equatorial pure states that contain equal contributions from the states in the coherence. We then use this framework to show how one can obtain a more accurate, but computationally more expensive, approximation to the third-order 2DES response function by replacing Ehrenfest dynamics with spin mapping during the pump-probe delay time. We end by comparing and contrasting the accuracy of these methods and the simpler mean classical path approximation in reproducing the exact linear, pump-probe, and 2DES spectra of two Frenkel exciton models: a coupled dimer system and the Fenna-Matthews-Olson complex.

The photodissociation dynamics of the smallest energized Criegee intermediate, H2COO, was characterized for vibrational excitation close to and a few kcal/mol above the barrier for hydrogen transfer. From an aggregate of at least 5 μs of molecular dynamics simulations using a neural network-representation of CASPT2/aug-cc-pVTZ reference data, the branching ratios into molecular products HCO + OH, CO2 + H2, or H2O + CO on the nanosecond time scale were quantitatively determined. Consistent with earlier calculations and recent experiments, decay into HCO + OH was found to be rare (∼2%), whereas the other two molecular product channels are accessed with fractions of ∼30% and ∼20%, respectively. On the 1ns time scale, which was the length of an individual molecular dynamics simulation, more than 40% of the systems remain in the reactant state due to efficient, partial intramolecular vibrational redistribution. Formation of CO2 + H2 occurs through a bifurcating pathway, one of which passes through formic acid, whereas the more probable route connects the di-radical OCH2O with the product through a low-lying transition state. Notably, none of the intermediates along the pathway accumulate, and their maximum concentration always remains well below 5%.

Efficient separation of hydrogen isotopes, especially H2 from D2, is critical for applications such as heavy-water production and fueling nuclear fusion. Achieving high selectivity at low energy cost remains a formidable challenge due to the isotopes' nearly identical physical properties. Metal-organic frameworks (MOFs) offer a promising low-energy, high-selectivity alternative for H2/D2 separation because their tunable porous structures can exploit subtle quantum effects. Here, we investigate how structural modifications to a prototypical MOF, FJI-Y11, influence its H2/D2 separation performance via quantum-sieving mechanisms. Using a suite of quantum and classical simulations, we show that subtle structural modifications, such as Zn substitution and Cl functionalization, significantly affect quantum sieving performance. In particular, the chloride functionalization synergistically enhances both zero-point-energy-driven adsorption affinity and confinement-driven quantum-exclusion mechanisms, markedly improving the H2/D2 selectivity. Our findings demonstrate that balancing pore size, framework flexibility, and adsorption-site chemistry can optimize hydrogen-isotope separation performance and guide the rational design of MOFs.

The five configurations of the complex between fullerene C60 and piperidine are bound mainly by C-H⋯C hydrogen bond, N-H⋯C hydrogen bond, C⋯N tetrel bond, lone pair⋯π interaction, and lone pair⋯σ interaction, respectively, thus making them good models for evaluating computational methods for noncovalent interactions between fullerenes and saturated organic molecules. The interaction energies of the five configurations of C60⋯piperidine were first calculated at the level of the coupled-cluster theory with single, double, and perturbative triple excitations [CCSD(T)] extrapolated to the complete basis set (CBS) limit. Using these CCSD(T)/CBS values as the benchmarks, we evaluated the accuracy of 53 popular low-cost computational methods, among which 49 methods were based on density functional theory (DFT). The results show that the accuracy of DFT-D4 is generally better than that of its predecessor DFT-D3. Surprisingly, even the most primitive DFT-D also consistently outperforms DFT-D3 in terms of accuracy. The ωB97M-V functional demonstrates the highest accuracy in the 53 popular low-cost computational methods, with absolute error magnitudes of the calculated interaction energies all less than 0.20 kcal/mol. The functionals B97M-V, ωB97X-V, B3LYP-D, ωB97X-D, B3LYP-D4, PBE0-D4, TPSS0-D4, X3LYP-D4, and CAM-B3LYP-D4 also show quite good computational accuracy, with absolute error magnitudes of their calculated interaction energies all less than 0.50 kcal/mol. This study lays a solid foundation for further computational investigations of noncovalent interactions between fullerenes and saturated organic molecules.

In this work, we studied the magnetization reversal (MR) phenomenon in the perovskite solid solution TmCr1-xCoxO3, where magnetic Cr3+ ions were substituted by non-magnetic low-spin (LS) Co3+ ions. Magnetic measurements and Monte Carlo (MC) simulations were performed following a field-cooling (FC) protocol. Samples of TmCr1-xCoxO3 with 0.1 ≤ x ≤ 0.8 were synthesized and structurally characterized. Samples with 0.1 ≤ x < 0.5 were synthesized at 1200 °C in the air atmosphere, while those with 0.5 ≤ x ≤ 0.8 were synthesized at 1000 °C under high O2 pressure. A model was implemented to simulate the FC magnetization curves, taking into account the coupling between Tm3+ and Cr3+ ions. This model is based on a classical Heisenberg spin Hamiltonian with realistic interactions. We showed that it is possible to reproduce the MR phenomenon with MC simulations in perovskite oxides with magnetic rare earth and transition metal sublattices. MC simulations accurately described all the FC curves except for x = 0.6 because this composition is near the percolation threshold, where fluctuations in the distribution of Co3+ ions can alter the magnetic properties. Another explanation could be a possible spin reorientation of the Cr3+ ions sublattice that makes experimental magnetization depart from the predicted one. In addition, it was found that the antiferromagnetic superexchange interactions between Cr3+ ions increase with Co3+ content.