Intermolecular Force Fields of Large Molecules by the Fragmentation Reconstruction Method (FRM):  Application to a Nematic Liquid Crystal

Abstract

A new intermolecular force field for the liquid-crystal-forming molecule 5CB (4-cyano, 4‘n-pentyl biphenyl) has been derived from two-body interaction energies, obtained by the fragmentation reconstruction method (FRM). The accuracy of this purely quantum mechanical approach has been verified by comparing FRM and directly ab initio computed interaction energies, obtaining a very satisfactory agreement with a maximum absolute error lower than 0.4 kcal/mol. The comparison was performed for a large number of internal geometries and dimer arrangements of two fragments of 5CB, namely, 4-cyano biphenyl (0CB) and n-pentyl benzene (5B). The potential energy surface of the 5CB dimer has then been used to parametrize a many-site model interaction potential suitable for computer simulations.

Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control

“…The geometry optimizations of the 2,4′ HQ / Q complex was carried out through the in house software Poldo 30 , which exploits the Fragmentation Reconstruction Method (FRM) 30 31 to compute the interaction energy. The latter was again computed at MP2/6–31G(0.25,0.44,0.37) level.…”

Atomistic simulations of liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2PhP and PhP14

“…This situation has been partially alleviated by the recent development of larger and faster computers, better parallel algorithms, 27 and more accurate force fields designed specifically for liquid crystals. [28][29][30][31][32][33] As a result, there have been a number of notable atomistic simulations of liquid crystals. 26,29,[33][34][35][36][37][38][39][40][41][42] Among these, only two have been performed on liquid crystal mixtures; one by Lansac et al on smectic mixtures of p,p -diheptylazobenzene (7AB) and 4-octyl-4 -cyanobiphenyl (8CB) molecules, 41 and the other by Pelaez and Wilson on a nematic mixture of E7, 42 which contains four components: 4-cyano-4 -n-pentyl-biphenyl (5CB), 4-cyano-4 -n-heptyl-biphenyl (7CB), 4-cyano-4 -n-octyloxy-biphenyl (80CB), and 4-cyano-4 -n-pentyl-p-terphenyl (5CT).…”

Potential energy surface of 4-hexyl-4′-cyanobiphenyl (6CB) on graphite surface: a DFT study with van der Waals corrections

“…The 6CB molecules are the simplest molecular structures in the cyanobiphenyl LCs, and this study is fundamentally important to extend the research to more complex LC molecules. Note: a The notations of atom are from Table 1 of Bizzarri et al [24], and the notation 'Cg' defined in this study indicates the carbon of graphite.…”

“…We used the same parameters as that determined by Bizzarri et al [24] for the 6CB molecules, and the parameters for the carbons of graphite were determined in this study. We used the modified DL_POLY_2 program [25] to calculate the PES using the force field.…”

“…The best-fit PES is shown in Figure 5, and the parameters are shown in Table 2. The parameters of 6CB molecule were kept to be equal to the model proposed by Bizzarri et al [24]. In this force-field model, we ignored the partial charge of the carbon atoms of graphite.…”