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VERSION:2.0
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DTSTAMP:20261021T085437Z
LAST-MODIFIED:20180411T164505Z
DTSTART:20180502T170000Z
DTEND:20180502T180000Z
UID:event1944@bu.edu
URL:http://physics.bu.edu/internal/events/show/1944
SUMMARY:A SUPERCOOLED STUDY OF NUCLEATION AND SYMMETRIES
DESCRIPTION:Featuring Rashi Verma\n\nPart of the PhD Final Oral Exams.\n\nE
	xamining Committee:  William Klein\, Harvey Gould\, Kevin Black\, Thomas Ke
	yes\, Rama Bansil\n\nAbstract:\n\nNucleation is the process by which a meta
	stable phase decays into a stable phase. It is\nwidely observed in nature\,
	 and is responsible for many phenomena such as the formation\nclouds and do
	mains in crystalline solids. The classical theory of nucleation predicts th
	at\nthe objects that initiate the decay from the metastable to the stable p
	hase are compact\ndroplets whose interior has the structure of the stable p
	hase. For quenches deep into the\nmetastable phase\, however\, the droplets
	 may be ramified\, with a structure very different\nfrom the stable phase. 
	This difference has profound implications for material properties\,\nespeci
	ally because predicting the onset of structure early enough is useful for m
	anipulating\nand controlling nucleation processes.\n\nI used molecular dyna
	mics to simulate nucleation in Lennard-Jonesium\, a model system for\nliqui
	d-solid transformations. The system is quenched from a high temperature\, w
	here the\nliquid is stable\, to a temperature where the liquid is metastabl
	e\, and is allowed to nucleate\nvia fluctuation-driven clusters referred to
	 as critical droplets. I determined the occurrence of\ncritical droplets by
	 the intervention method\, but found a non-monotonic variation in droplet\n
	survival rates near the saddle point. I determined the structure of the cri
	tical droplet and\nfound evidence for a core consisting of mostly solid-lik
	e particles with hcp symmetry and\na previously unknown planar structure ar
	ound it. Using perturbative techniques\, I showed\nthat the planar particle
	s have a significant influence on the nucleation and growth of critical\ndr
	oplets. I also introduced a novel method of learning symmetries to predict 
	the structure\nand appearance of precursors to the critical nucleus. My res
	ults give added evidence for the\npresence of spinodal nucleation at deep q
	uenches.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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