[Wien] Is calculating the chemical shielding (orbital part) in paramagnetic system using x_nmr_lapw available ? x_nmr_lapw? lapwdm? DIPAN?

[Peter Blaha]

You need to be carefully, what you mean by "paramagnetic system".

Most metals, even ths which never show any kind of magnetic order are 
paramagnetic (in the sence that an external field gets enhanced in the 
solid). Such systems you would do using x_nmr + Knight shift (+ dipol 
contr.)

Some metals are at low temperatures in an ordered magnetic phase. Above 
Tc or Tn the are also called paramagnets. However, there is a 
fundamental difference between such systems, because even above Tn or Tc 
local moments exist, but they are disorded.
In a first approximation we would simply ignore the fact that we are 
above Tc and calculate the ordered phase. In such cases you can use 
lapwdm, because the internal field (even without external field) is much 
larger than the induced one due to an external one.
A better way would be to introduce a supercell and use a "disordered 
moment model", where you randomly distribute spin-up and dn moments such 
that the total moment is zero.

And the last question:   The dipolar field from lapwdm is coming from 
the spin-density within the atomic sphere only.
Theinduced field from external moments is calculated by dipan.

Am 27.01.2020 um 18:04 schrieb 踢球者:
> Dear Wien experts,
> 
> Is calculating the chemical shielding (orbital part) in paramagnetic 
> system using x_nmr_lapw available ?
> 
> I suppose not after reading the UG carefully.
> 
> I find that, there is a program in WIEN2k, lapwdm.
> 
> "RINDEX=3 LSINDEX=3: <X> is the orbital part of the hyperfine field at 
> the nucleus (for a converged calculation at the very end)"
> Is this for chemical shielding ?
> 
> By the way, in this program: RINDEX=3 LSINDEX=5: <X> is the spin dipolar 
> part of the hyperfine field at the nucleus (for a converged calculation 
> at the very end). Here, what is the difference between DIPAN program 
> doing and "spin dipolar part of the hyperfine field" ?
> 
> About the DIPAN. Why I have to input spin moments of atoms?  Why not 
> calculating using spin density directly?
> 
> Best wishes,
> 
> Min
> 
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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