Ab initio ORTEP drawings: a case study of N-based molecular crystals with different chemical nature

Self Cite

Anisotropic displacement parameters (ADPs) are commonly used in crystallography, chemistry, and related fields to describe and quantify thermal motion of atoms. Within the very recent years, these ADPs have become predictable by lattice dynamics in combination with first-principles theory. Here, we study four very different molecular crystals, namely, urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene, by first-principles theory to assess the quality of ADPs calculated in the quasi-harmonic approximation. In addition, we predict both the thermal expansion and thermal motion within the quasi-harmonic approximation and compare the predictions with the experimental data. Very reliable ADPs are calculated within the quasi-harmonic approximation for all four cases up to at least 200 K, and they turn out to be in better agreement with the experiment than those calculated within the harmonic approximation. In one particular case, ADPs can even reliably be predicted up to room temperature. Our results also hint at the importance of normal-mode anharmonicity in the calculation of ADPs.

Section: Supplementary Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lattice thermal expansion and anisotropic displacements in urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene

George

Wang

Englert

et al. 2017

Self Cite

“…This method is commonly used in current work on ADP prediction. 13,16,[18][19][20] We have gathered experimental benchmark values at 100, 150, and 200 K using single-crystal XRD, and use these to assess our computed values at the different levels of theory (Fig. 4a).…”

Section: B Adps In the Harmonic Approximationmentioning

confidence: 99%

“…Therefore, the question arises whether the quality of the calculated ADP at this level of theory could be improved by considering volume expansion. To do so, we first attempt an ad-hoc improvement as discussed in earlier work 18 . Table 1).…”

Section: B Adps In the Harmonic Approximationmentioning

confidence: 99%

Lattice thermal expansion and anisotropic displacements in 𝜶-sulfur from diffraction experiments and first-principles theory

George

Deringer

Wang

et al. 2016

Self Cite

Thermal properties of solid-state materials are a fundamental topic of study with important practical implications. For example, anisotropic displacement parameters (ADPs) are routinely used in physics, chemistry, and crystallography to quantify the thermal motion of atoms in crystals. ADPs are commonly derived from diffraction experiments, but recent developments have also enabled their first-principles prediction using periodic density-functional theory (DFT). Here, we combine experiments and dispersion-corrected DFT to quantify lattice thermal expansion and ADPs in crystalline α-sulfur (S), a prototypical elemental solid that is controlled by the interplay of covalent and van der Waals interactions. We begin by reporting on single-crystal and powder X-ray diffraction measurements that provide new and improved reference data from 10 K up to room temperature. We then use several popular dispersion-corrected DFT methods to predict vibrational and thermal properties of α-sulfur, including the anisotropic lattice thermal expansion. Hereafter, ADPs are derived in the commonly used harmonic approximation (in the computed zero-Kelvin structure) and also in the quasi-harmonic approximation (QHA) which takes the predicted lattice thermal expansion into account. At the PPBE+D3(BJ) level, the QHA leads to excellent agreement with experiments. Finally, more general implications of this study for theory and experiment are discussed.

“…[28][29][30] The latter provide an easily interpretable view of the microscopic motion of atoms in solids 31 and can also provide thermodynamic information such as free energies 32 and heat capacities, 28,29 which can in turn be used to predict finite-temperature properties. 30,32 Latticedynamics calculations can also be used to model and interpret data from a range of routine experimental measurements with near-quantitative accuracy, 33,34 and thus can provide references to, for example, aid the use of quantitative spectroscopic techniques as a tool for characterising structural defects. 34 Whereas the performance of different DFT functionals in reproducing static properties has been well characterised, [35][36][37] the ability of common functionals to model lattice dynamics and finite-temperature structure and properties is poorly studied.…”

Section: Introductionmentioning

confidence: 99%

Influence of the exchange-correlation functional on the quasi-harmonic lattice dynamics of II-VI semiconductors

Skelton

Tiana

Parker

et al. 2015

Self Cite

104

We perform a systematic comparison of the finite-temperature structure and properties of four bulk semiconductors (PbS, PbTe, ZnS, and ZnTe) predicted by eight popular exchange-correlation functionals from quasi-harmonic lattice-dynamics calculations. The performance of the functionals in reproducing the temperature dependence of a number of material properties, including lattice parameters, thermal-expansion coefficients, bulk moduli, heat capacities, and phonon frequencies, is evaluated quantitatively against available experimental data. We find that the phenomenological over-and under-binding characteristics of the local-density approximation and the PW91 and Perdew-Burke-Enzerhof (PBE) generalised-gradient approximation (GGA) functionals, respectively, are exaggerated at finite temperature, whereas the PBEsol GGA shows good general performance across all four systems. The Tao-Perdew-Staroverov-Scuseria (TPSS) and revTPSS meta-GGAs provide relatively small improvements over PBE, with the latter being better suited to calculating structural and dynamical properties, but both are considerably more computationally demanding than the simpler GGAs. The dispersion-corrected PBE-D2 and PBE-D3 functionals perform well in describing the lattice dynamics of the zinc chalcogenides, whereas the lead chalcogenides appear to be challenging for these functionals.