Phenol hemihydrate: redetermination of the crystal structure by neutron powder diffraction, Hirshfeld surface analysis and characterization of the thermal expansion

Abstract

<jats:p>Phenol hemihydrate, C<jats:sub>5</jats:sub>H<jats:sub>5</jats:sub>OH·0.5H<jats:sub>2</jats:sub>O, crystallizes in the space group <jats:italic>Pbcn</jats:italic>, <jats:italic>Z</jats:italic> = 8. The previously published crystal structure [CSD refcode PHOLHH; Meuthen &amp; von Stackelberg (1960). <jats:italic>Z. Elektrochem</jats:italic>. <jats:bold>64</jats:bold>, 387–390] is shown to be incorrect. Pairs of phenol molecules, related by an inversion centre, are bridged by one water molecule <jats:italic>via</jats:italic> O—H...O hydrogen bonds; an extended <jats:italic>R</jats:italic> <jats:sup>4</jats:sup> <jats:sub>4</jats:sub>(8) hydrogen-bonded motif links these inversion dimers into chains parallel to the <jats:italic>c</jats:italic> axis. Packing of the chains is achieved by weaker T-shaped C—H...π interactions between nearest neighbour phenol molecules in the <jats:italic>bc</jats:italic> plane. Analysis of the thermal expansion and parameterization with a Debye model in terms of the linear elastic moduli shows that the <jats:italic>c</jats:italic> axis is ∼3 times stiffer than the two orthogonal directions.</jats:p>

Co-crystals, Salts, and Ionic Co-crystals of Ethanol and Ammonia

“…Figure 10 reports the principal linear expansivities and the volume thermal expansion coefficients of EMA and EHA derived using the methods outlined above. The values of V at high homologous temperatures, 5 -6 x10 −4 K −1 , are comparable with other simple alcohol hydrate crystals 3,36 but ~ 50 % greater than that found in methanol mono-ammoniate. 59 It is interesting to note the dramatic change in the thermal expansion of EHA above ~130 K, where both 1 and 2 increase sharply and 3 turns negative.…”

“…The 'PBE' gradient-corrected functional [33][34] was used in conjunction with the Tkatchenko & Scheffler (TS) dispersion correction 35 as this was found to provide accurate results in similar systems. 36 Structural relaxations were begun from the experimentally-obtained crystal structure using the BFGS method. 37 These were considered to have converged when the forces on each atom were less than 5x10 −3 eV Å −1 and each component of the stress tensor was smaller than 0.005 GPa.…”

“…Ultrasoft pseudopotentials with basis-set cut-offs of 1200 eV and k⃗ -point grids with reciprocal lattice spacings of ∼0.04 Å –1 (6 × 5 × 3 for EMA and 5 × 4 × 3 for EHA) were required to achieve convergence of better than 1 × 10 –2 GPa in the stress and better than 1 × 10 –3 eV per atom in total energy. The “PBE” gradient-corrected functional , was used in conjunction with the Tkatchenko & Scheffler (TS) dispersion correction as this was found to provide accurate results in similar systems . Structural relaxations were begun from the experimentally obtained crystal structure using the BFGS method .…”

Accurate H-atom parameters for the two polymorphs of L-histidine at 5, 105 and 295 K

“…Between 5 and 295 K, in both phases, there is an apparent decrease in the bond lengths, with the average values being À0.005 and À0.007 Å for the element-element and elementhydrogen bond lengths, respectively. This well-known effect occurs as a result of higher thermal motion at 295 K and is of clear relevance to studies that aim to 'benchmark' the performance of computational geometry optimization methods, many of which neglect thermal effects and refer to a nominal temperature of 0 K. The application of first-principles calculations, such as PBE-TS, to study the structure and properties of crystalline organic materials, has gained popularity in the past decade (Funnell et al, 2010(Funnell et al, , 2019Hunter et al, 2013;Moggach et al, 2015;Budd et al, 2015;Price et al, 2016;Fortes, 2020). A study performed seven years ago in our own laboratory (Binns et al, 2014) assessed the performance of DFT-D in reproducing the crystal structures of 30 small organic molecules.…”