scholarly journals Soft Crystal Force Field for Reproducing the Crystal Structures of Aryl Gold Isocyanide Complexes

2018 ◽  
Vol 17 (3) ◽  
pp. 155-157
Author(s):  
Naofumi NAKAYAMA ◽  
Shigeaki OBATA ◽  
Yoshikazu HORI ◽  
Hitoshi GOTO ◽  
Tomohiro SEKI ◽  
...  
Keyword(s):  
Force Field ◽  
Crystal Structures ◽  
Soft Crystal

Transferable force field for crystal structure predictions, investigation of performance and exploration of different rescoring strategies using DFT-D methods

2016 ◽  
Vol 72 (4) ◽  
pp. 460-476 ◽  
Author(s):  
Anders Broo ◽  
Sten O. Nilsson Lill
Keyword(s):  
Crystal Structure ◽  
Force Field ◽  
Crystal Structures ◽  
Density Functional ◽  
Geometry Optimization ◽  
Field Methods ◽  
Functional Theory ◽  
Ranking List ◽  
Drug Molecules ◽  
New Type

A new force field, here called AZ-FF, aimed at being used for crystal structure predictions, has been developed. The force field is transferable to a new type of chemistry without additional training or modifications. This makes the force field very useful in the prediction of crystal structures of new drug molecules since the time-consuming step of developing a new force field for each new molecule is circumvented. The accuracy of the force field was tested on a set of 40 drug-like molecules and found to be very good where observed crystal structures are found at the top of the ranked list of tentative crystal structures. Re-ranking with dispersion-corrected density functional theory (DFT-D) methods further improves the scoring. After DFT-D geometry optimization the observed crystal structure is found at the leading top of the ranking list. DFT-D methods and force field methods have been evaluated for use in predicting properties such as phase transitions upon heating, mechanical properties or intrinsic crystalline solubility. The utility of using crystal structure predictions and the associated material properties in risk assessment in connection with form selection in the drug development process is discussed.

Intermolecular Force-Field Parameters for Boron Hydrides

1998 ◽  
Vol 54 (1) ◽  
pp. 41-49 ◽  
Author(s):  
D. E. Williams ◽  
D. Gao
Keyword(s):  
Force Field ◽  
Ab Initio ◽  
Crystal Structures ◽  
Weighted Least Squares ◽  
Minimum Energy ◽  
Structural Parameter ◽  
Exponential Dependence ◽  
Monoclinic Space Group ◽  
Boron Hydrides ◽  
Force Field Parameters

Intermolecular atom–atom force-field parameters of the (exp-6-1) type for B and H atoms in boron hydrides were determined. They were obtained by full-weighted least-squares minimization of 116 forces in 15 observed crystal structures of boranes, the heat of sublimation of B10H14 and data from ab initio wavefunction calculations for diborane. Net atomic charges were obtained by fitting them to molecular electric potentials calculated from ab initio wavefunctions. Charges of terminal hydrogens were usually negative and those of bridging hydrogens usually positive. Repulsion-energy calculations for the B2H6 dimer provided the exponential dependence of H...H repulsion. Using the resulting force field, minimum-energy crystal structures were found with structural parameter values close to those of the observed structures. For diborane, energy minimization beginning with randomly oriented molecules placed initially in an 8 × 8 × 8 body-centered orthogonal cell led to the observed crystal structure and monoclinic space group.

scholarly journals An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics

2016 ◽  
Vol 72 (4) ◽  
pp. 477-487 ◽  
Author(s):  
Edward O. Pyzer-Knapp ◽  
Hugh P. G. Thompson ◽  
Graeme M. Day
Keyword(s):  
Force Field ◽  
Crystal Structures ◽  
Force Fields ◽  
Molecular Crystals ◽  
Intermolecular Force ◽  
Organic Molecular Crystals ◽  
Organic Solid ◽  
Lattice Energies ◽  
Validation Set ◽  
Unit Cell Dimensions

We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%.

Modelling the crystal structure of the 2-hydronitronylnitroxide radical (HNN): observed and computer-generated polymorphs

1999 ◽  
Vol 55 (4) ◽  
pp. 543-553 ◽  
Author(s):  
G. Filippini ◽  
A. Gavezzotti ◽  
J. J. Novoa
Keyword(s):  
Crystal Structure ◽  
Force Field ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Narrow Energy Range ◽  
Coulomb Type ◽  
Atomic Coordinates ◽  
Hydrogen Bonded

The crystal structures of two polymorphs of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (the 2-hydronitronylnitroxide radical, HNN) are analyzed by packing energy criteria. Other unobserved polymorphic crystal structures are generated using a polymorph predictor package and three different force fields, one of which is without explicit Coulomb-type terms. The relative importance of several structural motifs (hydrogen-bonded dimers, shape-interlocking dimers or extended hydrogen-bonded chains) is discussed. As usual, many crystal structures within a narrow energy range are generated by the polymorph predictor, confirming that ab initio crystal-structure prediction is still problematic. Comparisons of powder patterns generated from the atomic coordinates of the X-ray structure and from computational crystal structures confirm that although the energy ranking depends on the force field used, the X-ray structure of the \alpha polymorph was found to be among the most stable ones produced by the polymorph predictor, even using the chargeless force field.

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