Refinement of the structure of solid nitromethane

Treviño, S. F.; Prince, E.; Hubbard, Camden R.

doi:10.1063/1.440431

Cited by 129 publications

(113 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The crystal structure of d 3 -nitromethane has been the subject of numerous structural studies (David et al, 1992;Jeffrey et al, 1985;Trevino et al, 1980) that have focused on the large-amplitude curvilinear motion of the deuterium atoms in its methyl group. We have recently employed MD simulations to determine the experimental equilibrium structure of this molecule (Reilly et al, 2010b), showing highly anharmonic PDFs not only for the D atoms, as expected, but also for the O atoms at higher temperatures.…”

Section: Nitromethane and Ammoniamentioning

confidence: 99%

Using molecular-dynamics simulations to understand and improve the treatment of anharmonic vibrations. I. Study of positional parameters

Reilly¹,

Morrison²,

Rankin³

2011

Acta Cryst Sect A

View full text Add to dashboard Cite

Molecular‐dynamics‐derived numerical probability density functions (PDFs) have been used to illustrate the effect of different models for thermal motion on the parameters refined in a crystal structure determination. Specifically, anharmonic curved or asymmetric PDFs have been modelled using the traditional harmonic approximation and the anharmonic Gram–Charlier series treatment. The results show that in cases of extreme anharmonicity the mean and covariance matrix of the harmonic treatment can deviate significantly from physically meaningful values. The use of a Gram–Charlier anharmonic PDF gives means and covariance matrices closer to the true (numerically determined) anharmonic values. The physical significance of the maxima of the anharmonic distributions (the most probable or mode positions) is also discussed. As the data sets used for the modelling process are theoretical in origin, these most probable positions can be compared to equilibrium positions that represent the system at the bottom of its potential‐energy surface. The two types of position differ significantly in some cases but the most probable position is still worthy of report in crystal structure determinations.

show abstract

Section: Nitromethane and Ammoniamentioning

confidence: 99%

Using molecular-dynamics simulations to understand and improve the treatment of anharmonic vibrations. I. Study of positional parameters

Reilly¹,

Morrison²,

Rankin³

2011

Acta Cryst Sect A

View full text Add to dashboard Cite

show abstract

“…The space group is P2 1 2 1 2 1 with 28 atoms in the cell and experimental lattice vectors (taken at 4.2 K) of a = 5.183 Å, b = 6.236 Å, and c = 8.518 Å and lattice angles of α = β = γ = 90.0°. (Trevino et al, 1980) We tested for an appropriate k-point grid by running calculations at a kinetic energy cut-off of 545 eV with one (1x1x1), four (2x2x2), fourteen (3x3x3), and thirty-two (4x4x4) k-points with the PW91 functional.…”

Section: Nitromethanementioning

confidence: 99%

An ab Initio Study of Solid Nitromethane, HMX, RDX, and CL20: Successes and Failures of DFT

2004

View full text Add to dashboard Cite

Using the PW91 and PBE density functional theories (DFT), we have studied four energetic molecular crystals: nitromethane, HMX, RDX, and CL20 with a wide range of basis sets. Our goal is to assess the accuracy of DFT when applied to organic molecular crystals (such as energetic materials) as scientists are beginning to include this methodology in energetic materials research without knowledge of the limitations of the method. Intramolecular distances, simple angles, and band gaps are converged at plane wave cutoff energies (E cut ) of 430 to 495 eV. Cell parameters were determined over a range of E cut values from 280 eV to 700 or 800 eV, depending upon the system. Lattice vectors, however, display large errors in the range of 0.2 Å to 1.0 Å (up to a 9.6% error at the highest E cut used here), and a very slow convergence on basis set size. We hypothesize the error in the lattice vectors is due to a lack of van der Waals forces in current DFT functionals. This deficiency will have unforeseen consequences on all crystal calculations for organic molecules, and therefore caution should be employed whenever interpreting results obtained from the current DFT functionals available in solid state codes. To properly describe the electronic structure of these types of crystals, these results suggest the need for new methods involving DFT to be developed which include accurate dispersion forces.

show abstract

“…The absorption effect calculated from the Rouse, Cooper, York & Chakera (1970) approximation method for the observed ~tR = 0.33 is the same as the effect of an overall temperature factor B = -0.13 A 2. The refinement was carried out by means of a modification of the Rietveld (1969) method, which includes background intensity in the refinement (Trevino, Prince & Hubbard, 1980). Initial positions of H atoms were estimated from an idealized structure for the two amine groups.…”

mentioning

confidence: 99%

Refinement of 2-nitroguanidine by neutron powder diffraction

Choi¹

1981

Acta Crystallogr Sect B

View full text Add to dashboard Cite

Refinement of the structure of solid nitromethane

Cited by 129 publications

References 5 publications

Using molecular-dynamics simulations to understand and improve the treatment of anharmonic vibrations. I. Study of positional parameters

Using molecular-dynamics simulations to understand and improve the treatment of anharmonic vibrations. I. Study of positional parameters

An ab Initio Study of Solid Nitromethane, HMX, RDX, and CL20: Successes and Failures of DFT

Refinement of 2-nitroguanidine by neutron powder diffraction

Contact Info

Product

Resources

About