<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><DIV><BR>>Date: Wed, 24 Sep 2008 10:15:44 -0700<BR>>From: "Chih-Ying Lin" <<A href="mailto:chihying2008@gmail.com" ymailto="mailto:chihying2008@gmail.com">chihying2008@gmail.com</A>><BR>>Subject: [gmx-users] Forming a micelles<BR>>To: <A href="mailto:arun.target@gmail.com" ymailto="mailto:arun.target@gmail.com">arun.target@gmail.com</A><BR>>Cc: <A href="mailto:gmx-users@gromacs.org" ymailto="mailto:gmx-users@gromacs.org">gmx-users@gromacs.org</A><BR>>Message-ID:<BR>> <<A href="mailto:5777f3840809241015l2f0e85eo34dddc8f401864e1@mail.gmail.com" ymailto="mailto:5777f3840809241015l2f0e85eo34dddc8f401864e1@mail.gmail.com">5777f3840809241015l2f0e85eo34dddc8f401864e1@mail.gmail.com</A>><BR>>Content-Type: text/plain;
charset=ISO-8859-1<BR>><BR>>Hi<BR>>Would you please say more about your system?<BR>>How do you design / decide your simulation size of 100 surfactants +100<BR>>co-surfactants + 4000 water molecules??<BR>><BR>>How many surfactants will form a micelle?<BR>>How many atoms does one surfactant have?<BR>>How many atoms does one co-surfactant have?<BR>><BR>>Do you start from the critical micelle concentration?<BR>>You mentioned that it took 3 x 600 ps to see the micelles.<BR>>Do you mean that you have 3 computers to do the parallel simulation?<BR>><BR>>How long does it take to simulate 600 ps?<BR>>Do you visualize the whole 600 ps-image and SEE the micelle?<BR>>Or, other technique to KNOW the surfactants forming the micelles<BR>>without visualizing the system?<BR>><BR>>Thank you<BR>>Lin<BR>><BR>>******************************************</DIV>
<DIV>Dear Lin,</DIV>
<DIV>I have a suggestion:</DIV>
<DIV><BR>Micelles should (theoretically) form above the CMC. So if you want a micelle, the concentration should be >>CMC</DIV>
<DIV>I suggest that you find the CMC experimentally, then convert the concentration to nm^3 (let say: mv/1000nm^3)</DIV>
<DIV>The number of molecules should be able to obtained by multiplying with Avogadro number: (6.023x10^23). If your system contain co-surfactant, then you'll need to get the experimetal CMC for at least one of the two surfactants.Take a look at this paper: </DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 10pt 21.3pt; TEXT-INDENT: -21.3pt; LINE-HEIGHT: normal; TEXT-ALIGN: justify; mso-list: l0 level1 lfo1; tab-stops: 21.3pt"><SPAN style="FONT-FAMILY: 'Times New Roman'">Bourov G. K. and Bhattacharya A., Brownian dynamics of mixed surfactant micelles, <I style="mso-bidi-font-style: normal">Journal of Chemical Physics</I>, 123 (2005) 204712(1)-204712(6)<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN></P></DIV>
<DIV>How long 600 ps simulation is depends on your system size, box type, parameters and computational power (see manual).</DIV>
<DIV>One other way to KNOW the surfactants formed micelle is by measuring the surface tension (use g_energy). But g_energy gives surface*surface tension value, so you'll need to work on that. (HINT: Surface tension value drop drastically at CMC)</DIV>
<DIV> </DIV>
<DIV>Hope these helps,</DIV>
<DIV> </DIV>
<DIV>Muhammad Alif Mohammad Latif </DIV>
<DIV></DIV>
<DIV>Department of Chemistry<BR>Faculty of Science<BR>Universiti Putra Malaysia<BR>43400 UPM Serdang, Selangor<BR>MALAYSIA</DIV></div><br>
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