Theoretical study of structures of the X2CO and XYCO molecules (X and Y = H, F, or Cl) in the ground and lowest excited triplet electronic states

Abstract

Systematic calculations of the structures of the H2CO, F2CO, Cl2CO, HClCO, HFCO, and FClCO molecules in the S0 and T1 states were performed using the B3LYP and MP2 methods with different AO basis sets and also at the CCSD(T)/cc-pV(T+d)Z level of theory. The saturation of the correlation consistent sequence of basis sets cc-pV(N+d)Z (N = D, T, Q, and 5) and aug-cc-pV(N+d)Z (N = D, T, and Q) was studied. Recommendations for choosing the calculation method are given. The relativistic corrections were estimated. The influence of the number and type of halogen atoms on the geometric parameters of the molecules in the S0 and T1 states and the heights of inversion barriers in the T1 state was investigated.