d be the same
a non-coupled dimension (e.g. dimension z for xy option or any dimension
  for aniso option) can have 2 NULL values as specified pressures,
  which means apply no pressure control in that dimension (constant volume)
target pressure at intermediate points during a run is a ramped value
  between the beginning and ending pressure(s)
for nose/hoover style, frequency constant is like an inverse &quot;piston&quot; 
  mass which determines how rapidly the pressure fluctuates in response to a
  resto