Lattice thermal expansion and anisotropic displacements in urea, bromomalonic aldehyde, pentachloropyridine and naphthalene
arXiv:1705.10568 · doi:10.1063/1.4985886
Abstract
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 thermal expansion and thermal motion within the quasi-harmonic approximation and compare the predictions with 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 experiment than the harmonic ones. 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.
References in corpus (6)
- Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskites
- Anharmonicity in the high-temperature Cmcm phase of SnSe: soft modes and three-phonon interactions
- Neutron Diffraction Measurements and First Principles Study of Thermal Motion of Atoms in Select M_{n+1}AX_n and Binary MX Transition Metal Carbide Phases
- Raman spectroscopic features of the neutral vacancy in diamond from ab initio quantum-mechanical calculations
- First-principles investigation of the structural, dynamical and dielectric properties of kesterite, stannite and PMCA phases of Cu2ZnSnS4
- Lattice thermal expansion and anisotropic displacements in α-sulfur from diffraction experiments and first-principles theory