A study of I-h to T-h pseudo-Jahn-Teller (PJT) distortion in B-80 is presented. Reduced matrix elements for vibronic coupling and resulting force constants were calculated in I-h to elucidate the origin of B-80 symmetry breaking. Important orbital excitations involved are between inner orbitals 9h(g), 5h(g), and 6g(u) and virtual orbitals 8t(2u) and 8g(g). Low-lying occupied orbitals interact more strongly than frontier molecular orbitals due to their density distribution on the capping atoms. The large energy gaps, associated with these excitations, attenuate the PJT effect. The force constant calculations for B-80 point to a weak PJT energy stabilization of 304 cm(-1) at B3LYP/6-31G(d). (C) 2012 Elsevier B. V. All rights reserved.