Anisotropic displacement parameters from dispersion-corrected DFT methods and their experimental validation by temperature-dependent X-ray diffraction

Abstract

In chemical crystallography, the thermal motion of scattering centres is commonly described by anisotropic displacement parameters (ADPs). Very recently, it has been shown that ADPs are not only accessible by diffraction experiments but also via theory: this emerging approach seems promising but must be thoroughly tested. In this study, we have performed specifically tailored X-ray diffraction (XRD) experiments in fine steps between 100 and 300 K which allow detailed comparison to ab initio data from dispersion-corrected density functional theory (DFT) combined with periodic lattice-dynamics. The compound chosen for this study, crystalline pentachloropyridine IJC 5 NCl 5 ), is well suited for this purpose: it represents a molecular crystal without H atoms, thus posing no challenge to XRD; its solid-state structure is controlled by dispersion and halogen-bonding interactions; and the ADPs associated with the peripheral Cl atoms show strong temperature dependence. Quality criteria in direct and in reciprocal space prove that ADPs are predicted with high confidence for the temperature range between 100 and 200 K, and that several economic dispersion corrections to DFT can be reliably employed for this purpose. Within the limits we have explored here, the ab initio prediction of ADPs appears to be a facile and complementary tool, especially in those cases where diffraction data cannot provide a straightforward model for thermal motion.7414 | CrystEngComm, 2015, 17, 7414-7422This journal is

Anisotropic thermal motion in transition-metal carbonyls from experiments and ab initio theory

“…10 And likewise, it has very recently become possible to compute ADPs from first principles. [11][12][13] We used dispersion-corrected density functional theory (DFT-D) 18 to compute ADPs for representative carbonyl compounds of transition metals (Table 1) and validated the results against experimental benchmarks. We discuss the compounds in sequence and use each example to address pertinent questions regarding theoretical but also experimental aspects and limitations.…”

First Full Structural Characterization of Chloro Formamidinium Salts

“…Furthermore, Phonopy was used to calculate anisotropic displacement parameters (ADPs) for AuCCl 5 N 2 H 4 with a frequency cutoff of 0.1 THz and 34 × 26 × 18 q ‐points. In previous investigations, especially the ADPs of light atoms showed excellent agreement with experiment, and such theory‐derived ADPs have already been used in refining crystal structures. Likewise, they have also served as starting parameters in the evaluation of neutron powder diffraction data …”

[4‐(Ph3B)‐2,6‐Mes2Py]−: A Sterically Demanding Anionic Pyridine

“…The extended structures of the two compounds consist of alternating one‐dimensional chains showing short N ⋅⋅⋅ (halogen) contacts ( 2 ‐Cl: 308.4(1) pm; 2 ‐I: 294.2(1) pm). The crystal structure of unsubstituted 4‐chloropyridine has not been reported so far, however, the N ⋅⋅⋅ Cl contact found for pentachloropyridine is significantly shorter (293.5(1) pm) than the one found for 2 ‐Cl . In contrast, the N ⋅⋅⋅ I contact found for unsubstituted 4‐iodopyridine (298.8(5) pm) is slightly longer than the one found in 2 ‐I, which is surprising because of the bulky mesityl substituents at the 2,6‐positions.…”