Full-Dimensional Potential Energy and Dipole Moment Surfaces of GeH₄ Molecule and Accurate First-Principle...

Area of Science:

• Computational Chemistry
• Molecular Spectroscopy
• Quantum Chemistry

Background:

• Accurate theoretical models are essential for interpreting complex molecular spectra.
• Germane (GeH4) exhibits intricate vibrational and rotational spectra due to its stable isotopologues.

Purpose of the Study:

• To construct high-accuracy nine-dimensional potential energy surface (PES) and dipole moment surface (DMS) for germane.
• To enable accurate prediction of vibration-rotation spectra and line intensities for germane isotopologues.
• To investigate the role of isotopic shifts in germane spectra.

Main Methods:

• Ab initio coupled-cluster calculations with single, double, and perturbative triples (CCSD(T)) were performed at 19,882 points.
• Analytical representations of the PES and DMS were developed using expansions in symmetry-adapted coordinates.
• Nuclear motion variational calculations were employed to determine vibration-rotation line intensities.

Main Results:

• The PES achieved accuracy below 1 cm^-1 for experimental vibrational band centers of five germane isotopologues.
• Calculated rotational energies showed high accuracy for ⁷⁴GeH₄ and ⁷⁶GeH₄.
• First-time good agreement was achieved between calculated and experimental rotationally resolved spectra (700–5300 cm^-1).

Conclusions:

• The developed PES and DMS provide a highly accurate description of germane spectroscopy.
• Accurate modeling of state-dependent isotopic shifts is critical for interpreting germane spectra at natural isotopic abundance.
• The generated data will be accessible via the TheoReTS information system.