# nmr

Compute nuclear magnetic resonance (NMR) properties.

This command supports calculation of NMR shielding tensors at Hartree-Fock and DFT level of theories.

Below is an example input for calculating NMR shielding tensors on all nuclei of a water molecule at HF level of theory:

nmr(
structure( molecule = water )
hf(
ao = 'Def2-SVP'
)
)


We can also specify the indices of nuclei on which the NMR shielding is computed using atoms, for example,

nmr(
structure( molecule = water )
hf(
ao = 'Def2-SVP'
)
atoms = [1]
)


Alternatively, one can also specify the type of nuclei on which the NMR shielding is computed using type, for example,

nmr(
structure( molecule = water )
hf(
ao = 'Def2-SVP'
)
type = O
)


This command can appear in the global context.

### Options

atoms

Indices of atoms for which the NMR chemical shifts are computed. Note that indexing starts at 1. If not provided, the NMR chemical shifts are calculated for all nuclei.

• The type is [int]
• There is no default value.
• The value must be positive
convergence

Convergence threshold for the iterative subspace solver, tested on on the infinity norm of the residual vectors.

• The type is real
• The default is 1e-6
• The value must be positive
incore

Whether to use the incore algorithm to compute the NMR properties. The incore algorithm requires about 64 * N^3 GB of memory where N is the number of basis functions. Therefore, this is only recommended for small molecules.

• The type is bool
• The default is false
linear_dependency_threshold

Threshold for removing linearly dependent vectors based on the square of singular values of the matrix.

• The type is real
• The default is 1e-10
• The value must be positive
load

Name of result set from which to load orbitals from a previous dft or hf calculation.

• The type is string
• There is no default value.
max_iter

Maximum number of iterations for the iterative subspace solver.

• The type is int
• The default is 128
• The value must be positive
name

Specify the name of a set of results.

This option is deprecated.

• The type is string
• There is no default value.
orthonormal_threshold

Threshold for orthonormalization of the suspace vectors.

• The type is real
• The default is 1e-10
• The value must be positive
print_level

Print level.

• The type is int
• There is no default value.
• The value must be one of:
• -2 - No output
• -1 - Minimum output
• 0 - Output that doesn't scale with system size
• 1 - Output that scales linearly with system size
• 2 - (Debugging) output that scales quadratically with system size
• 3 - (Debugging) output that scales cubically with system size
spin_spin_coupling

Whether to compute indirect nuclear spin-spin coupling constants (i.e. the J-coupling constants).

• The type is bool
• The default is false
type

Specify the type of nuclei for which the NMR chemical shifts are computed.

• The type is string
• There is no default value.