QUAD EFG

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 V_zz (see LEFG values into the C_q often encountered in NMR literature. The conversion formula (Q is the element and isotope specific quadrupole moment):

{\displaystyle C_q = \frac{e Q V_{zz}}{h} }

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 C_q is in MHz. An online compilation of nuclear quadrupole moments can be found here.

Suppose a solid contains Al, C and Si, than the QUAD_EFG-tag could read:

QUAD_EFG = 146.6 33.27 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 it is pointless to calculate a C_q: again all stable isotopes have I≤1/2. No moments are known for the other isotopes.

Related Tags and Sections

LEFG

References

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