The instantaneous local magnetic fields depend on the conformation and surroundings of the molecule and can change in fluids very rapidly due to the molecular motions. However, the nuclear precession frequencies are usually much slower (∼ 10 1 -10 2 MHz) than the molecular tumbling. As a consequence, the observed Larmor frequencies are an average of the Larmor frequencies that the nucleus experiences during one period of its precession motion. This means that results of the quantum chemical calculations for properties, whose observation is associated with the precession of magnetization, need to be averaged for the nuclei that can, on the time scale of an NMR experiment, explore different conformations and hence different B loc and Larmor frequencies.