TNB : trinitrobenzene : SAPT(DFT) potential

Important

If you use this potential or any part of it please cite:

"A non-empirical intermolecular force-field for trinitrobenzene and its application in crystal structure prediction", A. A. Aina, A. J. Misquitta, and S. L. Price, J. Chem. Phys. 154, (2021) doi: 10.1063/5.0043746

Supplementary Information for this paper: TNB SI

Basic details

The non-empirical potential derivation begins from the isolated molecular structure of TNB obtained by optimising the isolated molecular conformation using the Gaussian09 program, with the PBE0 functional and the d-aug-cc-pVTZ Dunning basis. This molecular conformation was held rigid for the development of the force-fields and in all simulations, except those used to assess this approximation. The three non-empirical DIFF potentials were constructed using the workflow in Fig 2 of the above paper. These had the same long-range terms but differed in whether the short-range terms were isotropic, DIFF-srL0, or anisotropic with terms up to L = 2, DIFF-srL2. Additionally, the model parameters determined using first-order SAPT(DFT) energies were either allowed to relax against the total SAPT(DFT) intermolecular energies, indicated by “(rel),” or kept at their un-relaxed values, indicated by “(norel).” The comparisons were made with the non-empirical isotropic exp-6 model potential (FIT) whose parameters were fitted to organic crystal structures and have widely been used in CSP studies. The FIT model was either combined with multipoles computed using the Gaussian-Distributed Multipole Analysis (GDMA) method with the PBE0/6-31G(d,p) charge density, denoted as FIT(GDMA,L4), or the same ISA distributed multipoles used in the DIFF potentials [FIT(ISA,L4)]. Here, “L4” denotes that these multipoles contained terms of maximum rank of 4 on all sites.

Long-range terms

ISA: ISA-A algorithm in CamCASP 6.0 augA-Sadlej main basis with PBE0/CS00. Density fitting with aug-cc-pVTZ-RI basis and atom-auxiliary basis aug-cc-pVQZ-RI with s-functions replaced with ISA/set2 from CamCASP library.
ISA-DMA: Max rank 4 on all sites. ISA-GRID algorithm used based on above ISA solution.
ISA-Pol: Used for polarizabilities (kept to rank 1x1, ansiotropic) and dispersion coefficients (C6,C8,C10 from isotropic freq-dependent polarizabilities with max rank 3).

Short-range calculations

$E^{(1)}_{\rm elst}$ and $E^{(1)}_{\rm exch}$ computed on pseudo-random set of 2000 dimers.
Interaction energy including second-order terms computed using multiple sets of dimers as explained in the paper.