Question regarding electronic ground state

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Discussion Overview

The discussion revolves around the concept of the electronic ground state in quantum mechanics, specifically its implications for forces and torques acting on nuclei in a system. Participants explore the meaning of a statement regarding the absence of net force or torque when considering only the electronic ground state, referencing a specific paper on quantum mechanical stress and force.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants explain that the ground state of an atom is its lowest energy state, implying no interactions with other atoms, which relates to the absence of net force or torque on the nuclei.
  • One participant references a paper titled "Quantum mechanical stress and a generalized virial theorem for clusters and solids," indicating it provides a framework for understanding stress and force in quantum mechanics.
  • A participant mentions the Carr-Parinello quantum dynamics approach, which uses an extended Lagrangian to maintain electrons in the ground state, suggesting it yields results comparable to Born-Oppenheimer molecular dynamics with reduced computational costs.
  • Several participants seek clarification on the original statement, indicating a need for deeper understanding of the context and implications of the concepts discussed.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and seek clarification, indicating that the discussion remains unresolved with multiple interpretations and approaches to the topic.

Contextual Notes

Some participants express difficulties due to their backgrounds in mechanical engineering, highlighting potential limitations in understanding quantum mechanical concepts without a strong foundation in the subject.

chuckschuldiner
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hi can anyone please help me

I came across this statement "Since we only consider the electronic ground state of the system, there can be no net force or torque acting upon the subsystem of classically behaving nuclei". Can anyone explain what this means?
 
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The ground state of an atom refers to its lowest energy state. In other words, it is not interacting/reacting with other atoms. The net force or torque that is mentioned is referring to such interactions of the electrons.
 
chuckschuldiner said:
hi can anyone please help me

I came across this statement "Since we only consider the electronic ground state of the system, there can be no net force or torque acting upon the subsystem of classically behaving nuclei". Can anyone explain what this means?
Please tell us where you read this and in what chapter and what context.
 
scarecrow thanks but can u explain in some more detail?

gokul this is from a paper " quantum mechanical stress and a generalized virial theorem for clusters and solids", phys rev b vol 37 (pp 8167).

the paper deals with providing a quantum mechanical framework for stress and force but since i have a mech engg background i am having some difficulties. thanks for helping out
 
chuckschuldiner said:
hi can anyone please help me

I came across this statement "Since we only consider the electronic ground state of the system, there can be no net force or torque acting upon the subsystem of classically behaving nuclei". Can anyone explain what this means?
this is the basis of Carr-Parinello quantum dynamics - an extended langrangian is used to impose constraints that force the electrons into the ground state. it's gets results similar to born-oppenheimer MD at a fraction of the computational cost
 

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