Supplementary Materials for :
Conical Intersections between Vibrationally Adiabatic Surfaces in Methanol
Mahesh B. Dawadi and David S. Perry*
Department of Chemistry, The University of Akron, Akron, Ohio, 44325, United States
*Corresponding author. Email: dperry@uakron.edu.
Fig S1. A map in the 2-dimensional coordinate space of the COH bend angle  and the
torsional angle  showing the locations of the computed points and the conical
intersections. The red markers represent the conical intersections points with  = 0, 62˚
and 93˚. The blue markers represent the torsional saddle points, the green markers
represent the global minima points and the black markers are the computed points along
the MEP.
Fig. S2.
Variation of the computed frequencies of the two asymmetric CH stretch
vibrations of methanol along the minimum energy path (MEP). To obtain these CH
stretch frequencies, three different types of ab initio frequency calculations were carried
out: (i, upward pointing triangles) along the path of steepest descent from the torsional
saddle point (intrinsic reaction coordinate,“IRC”), a series of points with an 11dimensional normal mode analysis at each point, projecting out the reaction coordinate
itself, (ii, downward pointing triangles) along the same IRC path, ordinary 12dimensional (non-projected) normal mode analyses, and (iii, circular makers) at partially
optimized structures at a series of fixed torsional angles, ordinary 12-dimensional (non
projected) normal mode analyses. Calculation (i) is the same as was done by Xu et al.10,11
with the three-step G0912 procedure:
(a) MP2=Full/6-311+G(3df,2p), OPT=(Z-matrix,Vtight,TS,Nrscale,Noeigen) Nosymm,
(b) MP2=Full/6-311+G(3df,2p),Geom=check Nosymm IRC=(Stepsize=6,
Maxpoints=28,Forward,RCFC,Vtight), and (c) MP2=Full/6-311+G(3df,2p)
Freq=HPModes, where in step (c) the input geometries along the MEP are from the IRC
calculation (b) outputs. The projected vibrational frequencies along the MEP are given in
Table 5 of Ref. 10 in terms of Fourier expansion coefficients and values from those
Fourier coefficients are depicted in Fig. S2. The projected (i) and non-projected (ii) CH
stretch frequencies along the MEP are almost identical. In the partial optimization
procedure (iii), we used the same convergence criterion, basis set and theory level. For
each partially optimized geometry, the vibrational frequencies are plotted at the average
torsional angle  as defined in Ref. 10. At each torsional angle, the model calculation
(solid line, Eq. (3)) yields values between the MEP points, (i) and (ii), and the partially
optimized points (iii). The present model calculation agrees well with the XHL model as
represented in Fig. 9 of Ref.11.
Fig. S3. Methanol vibrational frequencies (a) and for the two asymmetric CH stretch
vibrations (2 A and 9 A ) and harmonic force constants (b) for individual CH bonds
computed at B3LYP/6-31+G(2d,p) OPT=(Z-matrix, tight) for eclipsed (e) and staggered
conformers (s). The figure and its labeling may be compared directly to the MP2 data in
Fig.1.