QUAD EFG: Difference between revisions
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Suppose a solid contains Al, C, and Si, then the {{TAG|QUAD_EFG}}-tag could read: | Suppose a solid contains Al, C, and Si, then the {{TAG|QUAD_EFG}}-tag could read: | ||
QUAD_EFG = 146.6 33.27 0 | QUAD_EFG = 146.6 33.27 0.0 | ||
<sup>27</sup>Al is the stable isotope of Al with a natural abundance of 100% and ''Q''=146.6. | <sup>27</sup>Al is the stable isotope of Al with a natural abundance of 100% and ''Q''=146.6. | ||
Latest revision as of 15:03, 27 February 2025
QUAD_EFG = [real array]
Default: QUAD_EFG = NTYP*1.0
Description: nuclear quadrupole moment (in millbarn) for the atomic types on the POTCAR file.
Setting the QUAD_EFG-tag allows the conversion of the Vzz (see LEFG) values into the quadrupole coupling constants Cq often encountered in NMR literature. The conversion formula is as follows (Q is the element and isotope specific quadrupole moment):
| Tip: Several definitions of are used in the NMR community. |
The QUAD_EFG-tag specifies the nuclear quadrupole moment in millibarns for each atomic species, in the same order as in the POTCAR file. The output Cq is in MHz. An online compilation of nuclear quadrupole moments can be found here or in Ref. [1] (updated numbers in Ref. [2]).
Suppose a solid contains Al, C, and Si, then the QUAD_EFG-tag could read:
QUAD_EFG = 146.6 33.27 0.0
27Al is the stable isotope of Al with a natural abundance of 100% and Q=146.6. The stable isotopes 12C and 13C are not quadrupolar nuclei, however, the radioactive 11C is. It has Q=33.27. For Si, all stable isotopes have I≤1/2, making it redundant to calculate a Cq. No moments are known for the other isotopes.
| Important: For heavy nuclei inaccuracies are to be expected because of an incomplete treatment of relativistic effects. |