<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div><span class="tab"> Hi!</span></div><div><span class="tab">I want to simulate an RNA molecule.</span></div><div><span class="tab">I have the .pdb file of that.</span></div><div><span class="tab">I want to create an Argon wall and make a hole on it to pull my molecule through it.</span></div><div><span class="tab">Argon defined in OPLS/AA force field. but it has not nucleic acids.</span></div><div><span class="tab">how can i define the argon in other force fields?<br></span></div></div></body></html>