Recent content by marie2010

Thanks for the reply. I am still, however, confused about the activity concept. So, does it measure the strength of interaction of the species? Why is it important to know it? Thanks.

hi, can someone help me in understanding the difference between chemical potential and activity? Why it is important to know/determine activities of certain species in material growth? Given that activity is dimensionless quantity, what is it measuring? Also, what is the activity of pure...

hi, I was reading an article about graphene and I came across some concepts I am not familiar with. I was just wondering if someone could help me understand them: The article says that charge carriers in graphene are massless fermions that are described with a Dirac-like equation rather than...

Thank you all or merci beaucoup... I get it now.

hi, thank you for the answer. So ( I just want to make sure I get it right), if we double or triple etc the unit cell, the condition for the forbidden reflection will be the same, i.e. h+2k=3n and l=odd and the conditions for the allowed reflections will not change as well. So, only the...

hi, when calculating conditions for Bragg reflections one usually works with a (1x1) cell. For example, for the hcp crystal lattice forbidden reflections are given by the condition h+2k= 3n and l=odd. Does it mean that if we double the cell, let's say to (2x2) the condition is h+2k=(3/2)n...

Hi, when doing MOCVD experiments one needs to control precursors' flow rates. What are the units of the flow (flux) and what are typical values for MOCVD growth of nitrides? Thanks for your help.

Thank you. I got it now.

Thank you for replying. Can you please help me understand the following: How come Nb5+ is d0 and diamagnetic, but Nb4+ is d1. I cannot see it. Thanks in advance.

hi, Can someone explain to me the difference between charge and spin ordering? How are they different and how are they related? I am very confused. Also, how are the bond lengths affected if an element is in 4+ as opposed to 5+ (e.g. Te4+ or Te5+ bonded to 6 oxygens). Are they...

hi, I still want to ask you the following: are only the 2nd order transitions reversible? What about the 1st order? I am trying to get some physical feel for how to distinguish between the transition orders and their significance, i.e. why is it important to know whether the transition was...

Thank you for your great explanation. It really helps.

hi, can someone explain to me how to distinguish (experimentally or theoretically) between 1st or 2nd (3rd?) order phase transformation in crystal structures. Thank you in advance.

Thank you all for replying. Reading the last post, I am confused about the following: So when you remove O from its site, do you take all its electrons with it (first reply to my original question), or leave them in the conduction band (last reply)? Or are we taking about the same thing? By...

Hello, revising the vacancy question, I have another one to ask: if we remove an O atom from its site taking all its electrons with it, the vacancy that was created would be a +2 vacancy. Does it mean that the system is charged now or it just "acts" like the charged one? Thanks.