The empirical equilibrium structure of diacetylene

TL;DR

This paper combines high-level quantum-chemical calculations with experimental data to determine the equilibrium structure and vibrational properties of diacetylene, achieving good agreement between theory and experiment.

Contribution

It provides a detailed empirical and theoretical analysis of diacetylene's structure and vibrational frequencies using advanced quantum chemistry methods.

Findings

Empirical equilibrium structure closely matches high-level theoretical calculations.

Computed vibrational frequencies agree satisfactorily with experimental data.

Detailed force fields for diacetylene are characterized.

Abstract

High-level quantum-chemical calculations are reported at the MP2 and CCSD(T) levels of theory for the equilibrium structure and the harmonic and anharmonic force fields of diacetylene, HCCCCH. The calculations were performed employing Dunning's hierarchy of correlation-consistent basis sets cc-pVXZ, cc-pCVXZ, and cc-pwCVXZ, as well as the ANO2 basis set of Almloef and Taylor. An empirical equilibrium structure based on experimental rotational constants for thirteen isotopic species of diacetylene and computed zero-point vibrational corrections is determined (r_e^emp: rC-H=1.0615 A, rCtripleC=1.2085 A, rC-C = 1.3727 A) and in good agreement with the best theoretical structure (CCSD(T)/cc-pCV5Z: rC-H=1.0617 Angstrom, rCtripleC=1.2083 A, rC-C=1.3737 A). In addition, the computed fundamental vibrational frequencies are compared with the available experimental data and found in satisfactory agreement.