Symmetry-Adapted Perturbation Theory Decomposition of the Reaction Force: Insights into Substituent Effects Involved in Hemiacetal Formation Mechanisms.

The decomposition of the reaction force based on symmetry-adapted perturbation theory (SAPT) has been proposed. This approach was used to investigate the substituent effects along the reaction coordinate pathway for the hemiacetal formation mechanism between methanol and substituted aldehydes of the form CXCHO (X = H, F, Cl, and Br), providing a quantitative evaluation of the reaction-driving and reaction-retarding force components. Our results highlight the importance of more favorable electrostatic and induction effects in the reactions involving halogenated aldehydes that leads to lower activation energy barriers.

Mapping the 3D orientation of piconewton integrin traction forces.

Mechanical forces are integral to many biological processes; however, current techniques cannot map the magnitude and direction of piconewton molecular forces. Here, we describe molecular force microscopy, leveraging molecular tension probes and fluorescence polarization microscopy to measure the magnitude and 3D orientation of cellular forces. We mapped the orientation of integrin-based traction forces in mouse fibroblasts and human platelets, revealing alignment between the organization of force-bearing structures and their force orientations.

Localized Intrinsic Valence Virtual Orbitals as a Tool for the Automatic Classification of Core Excited States.

Accurate assignments of the unoccupied molecular orbitals involved in electronic excitations are crucial to the interpretation of experimental spectra. Here we present an automated approach to the orbital assignment of excited states by introducing a unique orbital basis known as localized intrinsic valence virtual orbitals (LIVVOs), which are a special case of the previously reported valence virtual orbitals. The LIVVOs are used to quantify the local contributions to particle orbitals from orthogonality-constrained density functional theory, providing an assignment with atomic-level/angular momentum shell specificity.

Predicting Near Edge X-ray Absorption Spectra with the Spin-Free Exact-Two-Component Hamiltonian and Orthogonality Constrained Density Functional Theory.

Orthogonality constrained density functional theory (OCDFT) provides near-edge X-ray absorption (NEXAS) spectra of first-row elements within one electronvolt from experimental values. However, with increasing atomic number, scalar relativistic effects become the dominant source of error in a nonrelativistic OCDFT treatment of core-valence excitations. In this work we report a novel implementation of the spin-free exact-two-component (X2C) one-electron treatment of scalar relativistic effects and its combination with a recently developed OCDFT approach to compute a manifold of core-valence excited states.

Simulation of X-ray absorption spectra with orthogonality constrained density functional theory.

Orthogonality constrained density functional theory (OCDFT) [F. A. Evangelista, P.