NMRCOUPLING subkeys

The available switches within a NMRCOUPLING/END block control the computation of the NSSCCs. By default, the program will evaluate the FC coupling contribution for the first nucleus being the perturbing nucleus and all remaining nuclei responding. Please note that the ordering of atoms in CPL is generally different from the ADF input. Currently, there exists no workaround for this, but it will be available in future versions. The ordering of atoms is the one being stored in TAPE21 and it is grouped by fragment types. In case you are in doubt about the ordering of atoms, you can run CPL for a few seconds. It will print a list of atoms with their coordinates. The ordering is currently the same as required the NMR program in the ADF program system. Available subkeys are:

NMRCOUPLING
 NUCLEI {npert nresp1 nresp2}
 GAMMA {nnuc gamma}
 DSO
 PSO
 SD
 FC
 SCF {ITERATIONS=25 | NOCYCLE | CONVERGE=1e-4 }
 XALPHA
 CONTRIBUTIONS {1E19}
END

NUCLEI {npert nresp1 nresp2}
Use nucleus no. npert as the perturbing nucleus, and nuclei nresp1, nresp2, etc as responding nuclei. You can supply more than one NUCLEI keys, in which case CPL evaluates the first-order MOs for each perturbing nucleus that is specified and computes the NSSCCs between all specified responding nuclei. For each NUCLEI line in the input, CPL has to perform an SCF cycle.

GAMMA {nnuc gamma}
Input a non-default magneto-gyric ratio of g = gamma for nucleus no. nnuc, in units of 10⁷ rad/(T s). CPL normally uses the g value of the most abundant NMR active isotope for a nucleus of a given charge by default. With the GAMMA keyword you can override this value or supply a value if CPL does not know about it. A list of g's that is used in the computation is printed in the output. You have to provide the GAMMA key for each nucleus you want to specify.

DSO
Compute the diamagnetic orbital term for each NSSCC that is requested (not default)

PSO
Compute the paramagnetic orbital term for each NSSCC (not default)

SD
Compute the SD term for each NSSCC. This is only default for spin-orbit ADF runs. The output will contain the sum of the FC and SD contributions. Please note that requesting this option results in a greatly increased computational cost in scalar or non-relativistic runs. The option NOSD will turn the SD computation off in spin-orbit runs and has no effect otherwise.

FC
Compute the FC contribution to the NSSCCs. This is the default option. Please note that it is currently not possible to compute the SD term without the FC term. Consult the 'practical aspects' section for instructions how to estimate the FC/SD cross term. The option NOFC will disable both the FC and SD computation.

SCF options
Settings related to the SCF cycle that is carried out by CPL. Valid options are (with default values if applicable):

ITERATIONS 25
maximum number of iterations
NOCYCLE
perform no cycle, equivalent to ITERATIONS 0
CONVERGE 1e-4
convergence criterion, an input of e corresponds approximately to a convergence of log(-e) digits, i.e. the results will be converged to about four significant digits by default. The measurement for the convergence is based on the sum S of the magnitudes of all occupied-virtual matrix elements of the induced first-order exchange potential. Note that the actual convergence criterion being used in the computation is e times S of the first cycle, i.e. the convergence criterion is set relative to the initial value of S.

XALPHA
Use first-order Xalpha potential instead of VWN potential. This will usually decrease the accuracy for couplings involving hydrogen, and does not have a large effect for couplings between heavier nuclei (not default). The key is mainly intended to ensure compatibility with our previously published results.

CONTRIBUTIONS {1e19}
Print contributions from individual orbitals to the FC and OP term of the NSSCCs that are larger in magnitude than a certain threshold. The threshold refers to the reduced coupling constant K in SI units (not default).