B.6 Constants for unit conversion etc.
The following predefined constants are useful for conversion between units
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| Name | Value | Conversion from | Conversion to |
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| DEG2RAD | \(2 \pi / 360\) | Degrees | Radians |
| RAD2DEG | \(360 / (2 \pi )\) | Radians | Degrees |
| MIN2RAD | \(2 \pi / (360 \cdot 60)\) | Minutes of arc | Radians |
| RAD2MIN | \((360\cdot 60) / (2 \pi )\) | Radians | Minutes of arc |
| V2K | \(10^{-10} \cdot m_\mathrm {N}/\hbar \) | Velocity (m/s) | k-vector (Å\(^{-1}\)) |
| K2V | \(10^{10} \cdot \hbar / m_\mathrm {N}\) | k-vector (Å\(^{-1}\)) | Velocity (m/s) |
| VS2E | \(m_\mathrm {N} / (2 e)\) | Velocity squared (m\(^2\) s\(^{-2}\)) | Neutron energy (meV) |
| SE2V | \(\sqrt {2 e/m_\mathrm {N}}\) | Square root of neutron
energy (meV\(^{1/2}\)) | Velocity (m/s) |
| FWHM2RMS | \(1/\sqrt {8\log (2)}\) | Full width half maximum | Root mean square
(standard deviation) |
| RMS2FWHM | \(\sqrt {8\log (2)}\) | Root mean square
(standard deviation) | Full width half
maximum |
| MNEUTRON | \(1.67492 \cdot 10^{-27}\) kg | Neutron mass, \(m_\mathrm {n}\) | |
| HBAR | \(1.05459 \cdot 10^{-34}\) Js | Planck constant, \(\hbar \) | |
| PI | \(3.14159265...\) | \(\pi \) | |
| FLT_MAX | 3.40282347E+38F | a big float value | |
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