?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F29282%2F&rft.title=Computational+study+of+proton-disordered+ice+Ih&rft.creator=Wang%2C+Xun&rft.description=Water+is+the+most+important+liquid+on+the+earth%2C+yet+the+physics+behind+many+properties+of+water+is+still+poorly+understood.+Particular+interesting+are+the+condensed+phases+of+water%3A+ice+and+liquid+water%2C+that+both+possess+anomalous+properties.+In+this+thesis%2C+I+focus+on+using+different+methods%2C+including+force+fields+as+well+as+DFT+calculations%2C+to+predict+several+key+properties+of+proton-disordered+ice+Ih+and+liquid+water.%0D%0AThe+focus+of+my+study+of+ice+Ih+is+on+its+comparable+dielectric+constant+%CE%B5_s+with+liquid+water%2C+which+directly+results+from+its+proton-disorder+nature.+Predictions+of+the+dielectric+constant+of+ice+Ih+from+pairwise+additive+force+fields+fall+appreciably+below+than+the+experimental+values%2C+with+significant+improvement+being+achieved+by+polarizable+force+fields.+I+examined+the+performance+of+different+force+fields%2C+and+confirmed+that+the+polarizable+AMOEBA+models+with+three+polarizable+sites+per+molecule+outperform+polarizable+models+such+as+DC97+with+a+single+polarizable+site.%0D%0ASince+it+is+difficult+to+resolve+the+subtle+energetic+difference+of+different+proton+ordering+arrangements+in+ice+Ih+with+force+fields%2C+I+studied+the+energetics+of+ice+Ih%2C+from+DFT+calculations+using+the+BLYP+functional+as+well+as+several+dispersion-corrected+BLYP+functionals.+As+shown+in+my+study%2C+the+dispersion-corrected+functionals+not+only+give+better+energy+predictions+but+also+get+better+lattice+parameters+and+equilibrium+volumes+for+the+optimized+ice+Ih+unit+cells.+%0D%0AI+also+predicted+the+structural+as+well+as+dynamical+properties+of+liquid+water+from+ab+initio+molecular+dynamics+simulations+with+several+dispersion-corrected+BLYP+functionals.+The+results+of+calculations+all+confirmed+that+including+dispersion+corrections+in+functionals+is+essential+to+get+faster+water+rotational+dynamics+and+a+%E2%80%9Csofter%E2%80%9D+structure+of+liquid+water.+%0D%0AFinally+I+parametrized+a+two-channel+dispersion-corrected+atom-centered+pseudopotential+(DCACP2)+based+on+the+BLYP+functional+to+correct+for+the+long-range+dispersion+force+for+three+rare+gas+elements%3A+helium%2C+neon+and+argon.+By+fitting+the+interaction+energy+of+three+homonuclear+dimers+against+CCSD(T)+calculations%2C+the+resulting+DCACP2-BLYP+method+performs+significantly+better+than+the+one-channel+DCACP+approach+for+the+two-body+binding+energies+of+the+dimers.+I+also+explore+the+factor+responsible+for+the+success+of+DCACP2+method.&rft.date=2016-10-03&rft.type=University+of+Pittsburgh+ETD&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F29282%2F1%2Fxun-formatted_1.pdf&rft.identifier=++Wang%2C+Xun++(2016)+Computational+study+of+proton-disordered+ice+Ih.++Doctoral+Dissertation%2C+University+of+Pittsburgh.++++(Unpublished)++