Temperature effects in first-principles solid state calculations of the chemical shielding tensor made simple

Area of Science:

• Solid-state chemistry
• Computational materials science
• Quantum mechanics

Background:

• The chemical shielding tensor is crucial for understanding solid-state materials.
• Atomic vibrations influence electronic structure and thus chemical shielding.
• Accurate theoretical prediction of these effects is computationally demanding.

Purpose of the Study:

• To investigate the impact of atomic vibrations on the solid-state chemical shielding tensor.
• To compare the accuracy and efficiency of different computational methods for including vibrational effects.
• To propose a computationally feasible method for routine calculations.

Main Methods:

• First-principles density functional theory (DFT) calculations.
• Harmonic approximation using Monte Carlo (MC) and perturbative expansion methods.
• Investigation of zero-point quantum mechanical nuclear motion and anharmonic vibrations.

Main Results:

• Excellent agreement between MC and perturbative methods for isotropic shift and shielding anisotropy.
• Zero-point quantum mechanical nuclear motion significantly contributes to vibrational effects even at high temperatures (e.g., 500 K).
• Anharmonic vibrations have a minor impact on the zero-point correction to the chemical shielding tensor.

Conclusions:

• The perturbative expansion within the harmonic approximation is proposed as the method of choice for incorporating temperature effects.
• This approach offers accuracy comparable to more computationally expensive methods.
• The proposed method enables routine accounting for temperature effects in solid-state chemical shielding tensor calculations.