Long-standing problems associated with long-ranged electrostatic interactions have plagued theory and simulation alike. Traditional lattice sum (Ewald-like) treatments of Coulomb interactions add significant overhead to computer simulations and can produce artifacts from spurious interactions between simulation cell images. These subtle issues become particularly apparent when estimating thermodynamic quantities, such as free energies of solvation in charged and polar systems, to which long-ranged Coulomb interactions typically make a large contribution. In this paper, we develop a framework for determining very accurate solvation free energies of systems with long-ranged interactions from models that interact with purely short-ranged potentials. Our approach is generally applicable and can be combined with existing computational and theoretical techniques for estimating solvation thermodynamics. We demonstrate the utility of our approach by examining the hydration thermodynamics of hydrophobic and ionic solutes and the solvation of a large, highly charged colloid that exhibits overcharging, a complex nonlinear electrostatic phenomenon whereby counterions from the solvent effectively overscreen and locally invert the integrated charge of the solvated object.mean field theory | free energy calculations | density functional theory | hydrophobicity | solvation S olvation thermodynamics underlies a vast array of important processes, ranging from protein folding (1, 2) and ligand binding (3) to self-assembly at interfaces (4). Thus, understanding solvation, and driving forces rooted in solvation, has been a focus of chemistry and physics for over a century (5, 6).Quantitatively successful theories of self-solvation and solvophobic solvation in simple fluids have been developed (7-16). However, a generally useful analytic approach for solvation in complex charged and polar environments is lacking, and solvation is typically studied with computer simulations. Contributions from the long-ranged components of Coulomb interactions in periodic images of the simulation cell are typically evaluated using computationally intense Ewald and related lattice summation techniques (17). These methods generate distorted, system size-dependent interaction potentials (18) and do not scale well in massively parallel simulations (19), adding considerable computational overhead. Moreover, artifacts can arise from spurious interactions between the periodic images of solutes, as observed for proteins in water (20).The local molecular field (LMF) theory of nonuniform fluids is a promising avenue for substantially improving free energy calculations by removing many of the computational and conceptual burdens associated with long-ranged interactions (14,21). LMF theory prescribes a way to accurately determine the structure of a full system with long-ranged intermolecular interactions in a general single particle field by studying a simpler mimic system wherein particles interact with short-ranged intermolecular interactions only. An effective...

To bridge the gap between laboratory research and commercial applications, it is vital to develop scalable methods to produce large quantities of high-quality and solution-processable few-layer phosphorene (FLBP). Here, we report an ultrafast cathodic expansion (in minutes) of bulk black phosphorus in the nonaqueous electrolyte of tetraalkylammonium salts that allows for the high-yield (>80%) synthesis of nonoxidative few-layer BP flakes with high crystallinity in ambient conditions. Our detailed mechanistic studies reveal that cathodic intercalation and subsequent decomposition of solvated cations result in the ultrafast expansion of BP toward the high-yield production of FLBP. The FLBPs thus obtained show negligible structural deterioration, excellent electronic properties, great solution processability, and high air stability, which allows us to prepare stable BP inks (2 mg/mL) in low-boiling point solvents for large-area inkjet printing and fabrication of optoelectronic devices.

Complementary experimental and theoretical studies presented in this work examine the structure, organization, and solvating properties of methanol at a silica/methanol, solid/liquid interface. Findings from these experiments illustrate how strong association between a silica substrate and methanol solvent creates a distinctly nonpolar solvation environment for adsorbed solutes. Resonance-enhanced second-harmonic spectra and time-resolved fluorescence emission in a total internal reflection geometry both show that adsorbed solutes sample an interfacial environment having properties resembling those of a nonpolar solvent. Molecular dynamics simulations identify the origin of this effect. Strong hydrogen bonding between the first layer of methanol and silica’s silanol groups creates what is effectively a methyl-terminated surface that leads to a second layer having significantly reduced density and hydrogen bonding compared to bulk solution. The calculated solvent reorientation times in these first two layers is significantly slower than in bulk, implying slow dielectric relaxation and supporting both second-harmonic and time-resolved fluorescence results. Collectively, these studies illustrate how surface-induced changes in solvent structure change the chemistry at strongly associating solid/liquid interfaces as compared to bulk solution limits.

Orientational time correlation functions (TCFs) are derived for vibrational sum-frequency generation (VSFG) spectroscopy of the symmetric and asymmetric stretches of high-symmetry oscillators such as freely rotating methyl groups, acetylenic C-H groups, and cyanide groups. Molecular dynamics simulations are used to calculate these TCFs and the corresponding elements of the second-order response for acetonitrile at the liquid/vapor and liquid/silica interfaces. We find that the influence of reorientation depends significantly on both the functional group in question and the polarization conditions used. Additionally, under some circumstances, reorientation can cause the VSFG response function to grow with time, partially counteracting the effects of other dephasing mechanisms.