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Related Concept Videos

Calculating Standard Free Energy Changes02:49

Calculating Standard Free Energy Changes

26.6K
The free energy change for a reaction that occurs under the standard conditions of 1 bar pressure and at 298 K is called the standard free energy change. Since free energy is a state function, its value depends only on the conditions of the initial and final states of the system. A convenient and common approach to the calculation of free energy changes for physical and chemical reactions is by use of widely available compilations of standard state thermodynamic data. One method involves the...
26.6K
Gibbs Free Energy02:39

Gibbs Free Energy

40.8K
One of the challenges of using the second law of thermodynamics to determine if a process is spontaneous is that it requires measurements of the entropy change for the system and the entropy change for the surroundings. An alternative approach involving a new thermodynamic property defined in terms of system properties only was introduced in the late nineteenth century by American mathematician Josiah Willard Gibbs. This new property is called the Gibbs free energy (G) (or simply the free...
40.8K
Free Energy01:21

Free Energy

53.1K
Free energy—abbreviated as G for the scientist Gibbs who discovered it—is a measurement of useful energy that can be extracted from a reaction to do work. It is the energy in a chemical reaction that is available after entropy is accounted for. Reactions that take in energy are considered endergonic and reactions that release energy are exergonic. Plants carry out endergonic reactions by taking in sunlight and carbon dioxide to produce glucose and oxygen. Animals, in turn, break...
53.1K
Gibbs Free Energy and Thermodynamic Favorability02:23

Gibbs Free Energy and Thermodynamic Favorability

8.8K
The spontaneity of a process depends upon the temperature of the system. Phase transitions, for example, will proceed spontaneously in one direction or the other depending upon the temperature of the substance in question. Likewise, some chemical reactions can also exhibit temperature-dependent spontaneities. To illustrate this concept, the equation relating free energy change to the enthalpy and entropy changes for the process is considered:
8.8K
Free Energy and Equilibrium00:55

Free Energy and Equilibrium

9.7K
The free energy change for a process may be viewed as a measure of its driving force. A negative value for ΔG represents a driving force for the process in the forward direction, while a positive value represents a driving force for the process in the reverse direction. When ΔG is zero, the forward and reverse driving forces are equal, and the process occurs in both directions at the same rate (the system is at equilibrium).
The reaction quotient, Q, is a convenient measure of the...
9.7K
Free Energy and Equilibrium02:56

Free Energy and Equilibrium

28.1K
The free energy change for a process may be viewed as a measure of its driving force. A negative value for ΔG represents a driving force for the process in the forward direction, while a positive value represents a driving force for the process in the reverse direction. When ΔGrxn is zero, the forward and reverse driving forces are equal, and the process occurs in both directions at the same rate (the system is at equilibrium).
Recall that Q is the numerical value of the mass action...
28.1K

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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

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Exploring the free energy surface using ab initio molecular dynamics.

Amit Samanta1, Miguel A Morales1, Eric Schwegler1

  • 1Lawrence Livermore National Laboratory, Livermore, California 94550, USA.

The Journal of Chemical Physics
|May 2, 2016
PubMed
Summary
This summary is machine-generated.

This study shows how order-parameter aided sampling can efficiently explore material structures and identify metastable states. These methods systematically map free energy surfaces for materials like SiO2 and Ti.

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Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics
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Area of Science:

  • Computational materials science
  • Chemical physics
  • Condensed matter physics

Background:

  • Exploring configuration space and identifying metastable structures in condensed phases is computationally challenging.
  • Order-parameter aided sampling schemes are effective for exploring relevant configuration space.
  • Ab initio molecular dynamics (AIMD) provides a framework for simulating material behavior at the atomic level.

Purpose of the Study:

  • To demonstrate the application of order-parameter aided temperature accelerated sampling within AIMD frameworks.
  • To systematically explore free energy surfaces and identify metastable states and reaction pathways.
  • To investigate phase transitions and melting pathways in SiO2 and Ti.

Main Methods:

  • Utilizing order-parameter aided temperature accelerated sampling with Born-Oppenheimer and Car-Parrinello AIMD.
  • Applying the string method within density functional theory (DFT) calculations.
  • Identifying metastable structures and reaction pathways in SiO2 and Ti.

Main Results:

  • Successfully identified metastable structures and reaction pathways in SiO2 and Ti.
  • Investigated melting pathways in the high-pressure cotunnite phase of SiO2.
  • Studied the hexagonal closed packed (HCP) to face-centered cubic (FCC) phase transition in Ti.

Conclusions:

  • Order-parameter aided sampling schemes are efficient for exploring free energy surfaces and finding metastable states in condensed phase systems.
  • AIMD combined with order-parameter aided sampling provides a systematic approach for materials discovery.
  • The string method within DFT is effective for studying phase transitions and reaction pathways.