QUAD EFG: Difference between revisions
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Description: nuclear quadrupole moment (in millbarn) for the atomic types on the {{FILE|POTCAR}} file. | Description: nuclear quadrupole moment (in millbarn) for the atomic types on the {{FILE|POTCAR}} file. | ||
---- | ---- | ||
Setting the {{TAG|QUAD_EFG}}-tag allows the conversion of the ''V''<sub>zz</sub> (see {{TAG|LEFG}}) values into the ''C''<sub>q</sub> often encountered in NMR literature. | Setting the {{TAG|QUAD_EFG}}-tag allows the conversion of the ''V''<sub>zz</sub> (see {{TAG|LEFG}}) values into the quadrupole coupling constants ''C''<sub>q</sub> often encountered in NMR literature. | ||
The conversion formula is as follows (''Q'' is the element and isotope specific quadrupole moment): | The conversion formula is as follows (''Q'' is the element and isotope specific quadrupole moment): | ||
:<math> | :<math> | ||
C_q = \frac{e Q V_{zz}}{h}. | C_q = \frac{e Q V_{zz}}{h}. | ||
</math> | </math> | ||
{{NB|tip|Several definitions of <math> C_q</math> are used in the NMR community.}} | |||
The {{TAG|QUAD_EFG}}-tag specifies the nuclear quadrupole moment in millibarns for each atomic species, in the same | The {{TAG|QUAD_EFG}}-tag specifies the nuclear quadrupole moment in millibarns for each atomic species, in the same | ||
order as in the {{FILE|POTCAR}} file. The output ''C''<sub>q</sub> is in MHz. An online compilation of nuclear quadrupole moments can be found [http://www.chem.helsinki.fi/~pyykko/Q2008.pdf here] or in Ref. | order as in the {{FILE|POTCAR}} file. The output ''C''<sub>q</sub> is in MHz. An online compilation of nuclear quadrupole moments can be found [http://www.chem.helsinki.fi/~pyykko/Q2008.pdf here] or in Ref. {{Cite|pyykko:molphys:2008}} (updated numbers in Ref. {{Cite|pyykko:molphys:2017}}). | ||
Suppose a solid contains Al, C and Si, | 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. | ||
The stable isotopes <sup>12</sup>C and <sup>13</sup>C are not quadrupolar nuclei, however, the radioactive | The stable isotopes <sup>12</sup>C and <sup>13</sup>C are not quadrupolar nuclei, however, the radioactive | ||
<sup>11</sup>C is. It has ''Q''=33.27. For Si it | <sup>11</sup>C is. It has ''Q''=33.27. For Si, all stable isotopes have I≤1/2, making it redundant to calculate a ''C''<sub>q</sub>. No moments are known for the other isotopes. | ||
{{NB|important|For heavy nuclei inaccuracies are to be expected because of an incomplete treatment of relativistic effects.}} | |||
== Related tags and articles == | == Related tags and articles == | ||
{{TAG|LEFG}} | {{TAG|LEFG}} | ||
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== References == | == References == | ||
[[Category:INCAR tag]][[Category:NMR | [[Category:INCAR tag]][[Category:NMR]] | ||
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. |