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- Shikha Nangia, Barbara J. Garrison
- The journal of physical chemistry. A
- 2008

In this computational study, we present the dissolution rates for quartz as a function of pH at 298 K. At any given pH, the dissolution of the quartz surface depends on the distribution of protonated, deprotonated, or neutral species. The dissolution mechanism for each of these three species was investigated by ab initio electronic structure calculations toâ€¦ (More)

- Christin P Morrow, Shikha Nangia, Barbara J. Garrison
- The journal of physical chemistry. A
- 2009

The reactions of aluminosilicate clusters with water are investigated using ab initio calculations. There are several reaction sites on a mineral surface, and, in the case of aluminosilicates, the dissolution chemistry is dictated by chemically distinct surface termination sites: Al and Si. Environmental factors such as pH determine the protonation stateâ€¦ (More)

- Shikha Nangia, Barbara J. Garrison
- Journal of the American Chemical Society
- 2009

A newly developed Monte Carlo (MC) algorithm designed to study the complex interplay of dissolution and precipitation reactions on mineral surface is presented. This algorithm utilizes existing advanced reactive and configurational-biased MC techniques with new protocols specific for mineral-water interfaces. This time-independent methodology is especiallyâ€¦ (More)

- Shikha Nangia, Donald G. Truhlar, Michael J. McGuire, Piotr Piecuch
- The journal of physical chemistry. A
- 2005

We calculated the two lowest electronically adiabatic potential energy surfaces of ammonia in the region of the conical intersection and at a sequence of geometries along which one of the N-H bonds is broken. We employed both a multireference (MR) method and a single-reference (SR) method. The MR calculations are based on multiconfiguration quasidegenerateâ€¦ (More)

- Chaoyuan Zhu, Shikha Nangia, Ahren W Jasper, Donald G. Truhlar
- The Journal of chemical physics
- 2004

The self-consistent decay-of-mixing (SCDM) semiclassical trajectory method for electronically nonadiabatic dynamics is improved by modifying the switching probability that determines the instantaneous electronic state toward which the system decoheres. This method is called coherent switching with decay of mixing (CSDM), and it differs from the previouslyâ€¦ (More)

- Shikha Nangia, Ahren W Jasper, Thomas F Miller, Donald G. Truhlar
- The Journal of chemical physics
- 2004

The most widely used algorithm for Monte Carlo sampling of electronic transitions in trajectory surface hopping (TSH) calculations is the so-called anteater algorithm, which is inefficient for sampling low-probability nonadiabatic events. We present a new sampling scheme (called the army ants algorithm) for carrying out TSH calculations that is applicableâ€¦ (More)

- Shikha Nangia, Ahren W Jasper, Thomas F Miller, Donald G. Truhlar
- The Journal of chemical physics
- 2016

- Shikha Nangia, Donald G. Truhlar
- The Journal of chemical physics
- 2006

We used multiconfiguration quasidegenerate perturbation theory and the fourfold-way direct diabatization scheme to calculate ab initio potential-energy surfaces at 3600 nuclear geometries of NH3. The calculations yield the adiabatic and diabatic potential-energy surfaces for the ground and first electronically excited singlet states and also the diabaticâ€¦ (More)

- Ahren W Jasper, Shikha Nangia, Chaoyuan Zhu, Donald G. Truhlar
- Accounts of chemical research
- 2006

Electronically nonadiabatic or non-Born-Oppenheimer (non-BO) chemical processes (photodissociation, charge-transfer, etc.) involve a nonradiative change in the electronic state of the system. Molecular dynamics simulations typically treat nuclei as moving classically on a single adiabatic potential energy surface, and these techniques are not immediatelyâ€¦ (More)

- Ahren W Jasper, Chaoyuan Zhu, Shikha Nangia, Donald G. Truhlar
- Faraday discussions
- 2004

Recent progress in the theoretical treatment of electronically nonadiabatic processes is discussed. First we discuss the generalized Born-Oppenheimer approximation, which identifies a subset of strongly coupled states, and the relative advantages and disadvantages of adiabatic and diabatic representations of the coupled surfaces and their interactions areâ€¦ (More)

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