[CP2K-user] [CP2K:18067] Units for NMR Shift

[Ronald Cohen]

I am struggling with the lack of documentation for the NMR calculations. 
What are the units in the SHIFT files? I find:

! Conversion factors
*      ! factor for the CHEMICAL SHIFTS: alpha^2 *  ppm.*
*      nmr_env%shift_factor = (1.0_dp/137.03602_dp)**2*1.0E+6_dp/cell%deth*
*      ! factor for the CHEMICAL SHIFTS: alpha^2 *  ppm.*
*      nmr_env%shift_factor_gapw = (1.0_dp/137.03602_dp)**2*1.0E+6_dp*
      ! chi_factor =  1/4 * e^2/m * a_0 ^2
      nmr_env%chi_factor = 1.9727566E-29_dp/1.0E-30_dp ! -> displayed in 
10^-30 J/T^2
      ! Factor to convert 10^-30 J/T^2 into ppm cgs = ppm cm^3/mol
      ! = 10^-30 * mu_0/4pi * N_A * 10^6 * 10^6  [one 10^6 for ppm, one for 
m^3 -> cm^3]
      nmr_env%chi_SI2ppmcgs = 6.022045_dp/1.0E+2_dp
      ! Chi to Shift: 10^-30  *  2/3  mu_0 / Omega  * 1/ppm
      nmr_env%chi_SI2shiftppm = 1.0E-30_dp*8.37758041E-7_dp/ &
                                (cp_unit_from_cp2k(cell%deth, 
"angstrom^3")*1.0E-30_dp)*1.0E+6_dp

      IF (output_unit > 0) THEN
         WRITE (output_unit, "(T2,A,T65,ES15.6)") "NMR| Shift gapw radius 
(a.u.) ", nmr_env%shift_gapw_radius
         IF (nmr_env%do_nics) THEN
            WRITE (output_unit, "(T2,A,T50,I5,A)") "NMR| NICS computed in 
", nmr_env%n_nics, " additional points"
            WRITE (output_unit, "(T2,A,T60,A)") "NMR| NICS coordinates read 
on file ", TRIM(nics_file_name)
         END IF
         WRITE (output_unit, "(T2,A,T65,ES15.6)") "NMR| Shift factor 
(ppm)", nmr_env%shift_factor
         IF (gapw) THEN
            WRITE (output_unit, "(T2,A,T65,ES15.6)") "NMR| Shift factor 
gapw (ppm)", nmr_env%shift_factor_gapw
         END IF
         WRITE (output_unit, "(T2,A,T65,ES15.6)") "NMR| Chi factor (SI)", 
nmr_env%chi_factor
         WRITE (output_unit, "(T2,A,T65,ES15.6)") "NMR| Conversion Chi 
(ppm/cgs)", nmr_env%chi_SI2ppmcgs
         WRITE (output_unit, "(T2,A,T65,ES15.6)") "NMR| Conversion Chi to 
Shift", nmr_env%chi_SI2shiftppm
      END IF

And in the output of that run:

        Inizialization of the NMR environment

 NMR| Shift gapw radius (a.u.)                                     
1.133836E+02
 NMR| Shift factor (ppm)                                           
6.533065E-03
 NMR| Shift factor gapw (ppm)                                     
 5.325134E+01
 NMR| Chi factor (SI)                                             
 1.972757E+01
 *NMR| Conversion Chi (ppm/cgs)                                     
6.022045E-02*
* NMR| Conversion Chi to Shift                                     
 6.935882E-04*

So to convert the numbers in the SHIFT files is the correct conversion is 
*6.022045E-02 or **6.935882E-04? *

*Thank you!*

*Sincerely,*

*Ron Cohen*


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