Fifty Shades of Water: Benchmarking DFT Functionals against Experimental Data for Ionic Crystalline Hydrates

Abstract

We propose that crystalline ionic hydrates constitute a valuable resource for benchmarking theoretical methods for aqueous ionic systems. Many such structures are known from the experimental literature, and they contain a large variety of water–water and ion–water structural motifs. Here we have collected a data set (CRYSTALWATER50) of 50 structurally unique “in-crystal” water molecules, involved in close to 100 nonequivalent O–H···O hydrogen bonds. A dozen well-known DFT functionals were benchmarked with respect to their ability to describe these experimental structures and their OH vibrational frequencies. We find that the PBE, RPBE-D3, and optPBE-vdW methods give the best H-bond distances and that anharmonic OH frequencies generated from B3LYP//optPBE-vdW energy scans outperform the other methods, i.e., here we performed B3LYP energy scans along the OH stretching coordinate while the rest of the structure was kept fixed at the optPBE-vdW-optimized positions.

Quantitative and qualitative performance of density functional theory rationalized by reduced density gradient distributions

“…This means that a functional that without dispersion correction underestimates energetic properties and overestimates structural properties will benefit from the a posteriori correction, while the opposite holds for vice versa. Similar observations have been seen for crystalline hydrates [43]. However, it is unclear if this conclusion can be generalized to all a posteriori methods.…”

“…We validated our choices by performing tests on selected properties using the vdW-DF-cx functional. Lately, it has been noted that for many systems, hard pseudopotentials and high cutoff energies are needed to converge properties calculated using the vdW-DF type of functionals, see, e.g., Kebede et al studying crystalline hydrates [43], Granhed et al studying BaZrO 3 [44], and Vlaisavljevich et al studying metal-organic frameworks [45]. In these studies, cutoff energies up to 1600 eV were used and were deemed necessary to converge certain properties.…”

Vanadium Pentaoksida (V2O5) : Termodinamika Molecular dan Interaksi Ion dalam Larutan

“…Pergerakan vanadium pentaoksida di dalam larutan cukup reaktif, karena adanya unsur asam yang berlebih, sehingga ketika dicampurkan dengan senyawa lain akan membentuk senyawa asam (122)(123)(124)(125)(126)(127)(128) berlebih dan tergantung dari senyawa yang dicampurkan, serta dapat memberikan ikatan ionic (129)(130)(131) berupa anion dan kation dalam larutan.…”

Studi Termodinamika Transpor Ionik Natrium Klorida Dalam Air dan Campuran Tertentu

“…ClNa Sodium chloride atrium klorida memiliki bentuk kristal berwarna putih dengan struktu adalah kubus yang berpusat pada wajah. Natrium klorida dapat dalam air (160) jika dilarutkan dengan perbandingan pelarut yang lebih ambar 3. Analisis molekul NaCl menggunakan ChemDraw Ultra Version 15, Perkinelmer Informatic.…”