n>;    <span class="comment">% threshold surface separation distance to include particles in the verlet list</span>
        verlet_freq <span class="string">uint32</span>  <span class="string">=</span> <span class="string">uint32.empty</span>;    <span class="comment">% verlet list update frequency (in steps)</span>
        auto_freq   <span class="string">logical</span> <span class="string">=</span> <span class="string">logical.empty</span>;   <span class="comment">% flag for automatic setting the update f