Table 7 The experimental values of the force constants of protons, carbon, and nitrogen nuclei for the powder sample of melamine of mass M = 2.298 g contrasted with the ab initio predictions from the HLD simulations, both obtained using Eq. (21).

From: Non-invasive detection of hazardous materials with a thermal-to-epithermal neutron station: a feasibility study towards practical application

Nucleus

HLD prediction

Multivariate Gaussian fit

Isotropic Gaussian fit

 

\(\sigma _x\)

\(\sigma _y\)

\(\sigma _z\)

\(\sigma _x\)

\(\sigma _y\)

\(\sigma _z\)

\(\sigma \)

H

0.160

0.161

0.160

0.159 ± 0.001

0.160± 0.001

0.160± 0.001

–

C

1.918

1.918

1.918

–

–

–

1.918 ± 0.001

N

2.238

2.238

2.238

–

–

–

2.238 ± 0.001

  1. In the case of protons, both experimental and simulated values are obtained from the multivariate Gaussian model of the nuclear momentum distribution using Eq. 21. In the case of carbon and nitrogen, the values listed are calculated based on the isotropic Gaussian model for the NMD. Force constant values are given in units of eV/Å.
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