Character of intermolecular vibrations in the benzene–neon complex based on CCSD(T) and SAPT potential energy surfaces

Abstract

The intermolecular potential energy surface of the benzene-neon complex is constructed using highly accurate electronic structure methods for the ground electronic ground state. The interaction energies have been calculated with...

Ab Initio Potentials for the Ground S0 and the First Electronically Excited Singlet S1 States of Benzene–Helium with Application to Tunneling Intermolecular Vibrational States

“…We used the same ground state benzene geometry from ref as previously for other BzRg complexes. ,− The ground state bond lengths were 1.3915 Å for CC and 1.080 Å for CH bonds. The excited state S 1 geometry was taken from ref with bond lengths of 1.430 Å for CC and 1.085 Å for CH bonds.…”

“…In this case the potential can be written as follows: V int ( R ) = V sr ( R ) + V lr ( R ) The long-range potential can be presented using the form V lr ( R ) = prefix− ∑ n = 6 10 ∑ l , m f n lr ( R ) C n l , m R n normalΩ l m ( θ , φ ) where it is reasonable to take 1/ R n up to n = 10 for accurate reproduction of the long-range potential and the terms with ( l , m ) = (0, 0), (2, 0), (4, 0), (6, 0), (6, 6) due to benzene symmetry. The term with n = 6 describes the dispersion coupling of induced dipole polarizabilities of the monomers and the terms with n = 8 dipole–quadrupole and n = 10 quadrupole–quadrupole couplings . In order to guarantee vanishing of V lr ( R ) in the short-range regions, the expansion terms have to multiplied by damping functions f n ( R ).…”

“…Here r k is the distance between an atom and k th atom of an aromatic molecule, and a k and r ke are some parameters found from nonlinear optimization fitting algorithm. Such an approach was recently applied by us for a series of similar complexes. − It can be written as follows: V sr ( R ) = h sr ( R ) [ V 0 + W 0 false( prefix∑ k V 2 ( r k ) + prefix∑ l < k V 3 ( r k , r l ) false) ] In eq the two-body terms V 2 are defined as V 2 ( r k ) = w 2 ( r k ) + prefix∑ i > 2 c i w i ( r k ) and three-body terms as …”

“…Here r k is the distance between an atom and k th atom of an aromatic molecule, and a k and r ke are some parameters found from nonlinear optimization fitting algorithm. Such an approach was recently applied by us for a series of similar complexes. − It can be written as follows: In eq the two-body terms V 2 are defined as and three-body terms as The constants V 0 and W 0 are chosen manually to reproduce ab initio E int with maximum accuracy.…”

“…In contrast to BzRg with heavier than He atoms, , the assignment of the vibrational states in terms of the harmonic oscillator quantum numbers ( n s , n b , l ) for the singly degenerate stretching mode n s and the doubly degenerate bending mode ( n b , l ) can only be done formally. The states 2 A 1 ′ /2 A 1 ″ and 1 E 1 ′ /1 E 1 ″ in Table are approximately identified as the lowest stretching and bending modes, respectively.…”