# In thermodynamic the work done is PdV than what is the meaning of VdP?

SAGAR SINGH - IIT DELHI
878 Points
13 years ago

Dear student,

H = U + PV

G = A + PV

In differential form we have

dH = dU + PdV + VdP = TdS + VdP

dG = dA + PdV + VdP = -SdT + VdP

Free energy functions are at the heart of chemical thermodynamics. They describe the spontaneous direction for a process in terms of the heat released by a reaction (DH) and the entropy change in the system (DS). If the heat exchanged with the surroundings creates a greater disorder in the surroundings than the order in the system created during the process, then it will be spontaneous. Understanding free energy is important in the context of molecular dynamics simulations. The potential energy surface defined by the individual terms (i.e. bond stretching, angle bending, torsions, and van der Waals) gives the contribution to the internal energy, but does not say anything about the entropy. The entropy is proportional to the number of states accessible to the system, and by the ergodic hypothesis that can be sampled by allowing a simulation to run for an infinitely long period of time and counting the states. Thus, our estimate of the entropy will be the weakest aspect of a computer simulation.

All the best.

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Sagar Singh

B.Tech, IIT Delhi

H = U + PV

G = A + PV

In differential form we have

dH = dU + PdV + VdP = TdS + VdP

dG = dA + PdV + VdP = -SdT + VdP

Free energy functions are at the heart of chemical thermodynamics. They describe the spontaneous direction for a process in terms of the heat released by a reaction (DH) and the entropy change in the system (DS). If the heat exchanged with the surroundings creates a greater disorder in the surroundings than the order in the system created during the process, then it will be spontaneous. Understanding free energy is important in the context of molecular dynamics simulations. The potential energy surface defined by the individual terms (i.e. bond stretching, angle bending, torsions, and van der Waals) gives the contribution to the internal energy, but does not say anything about the entropy. The entropy is proportional to the number of states accessible to the system, and by the ergodic hypothesis that can be sampled by allowing a simulation to run for an infinitely long period of time and counting the states. Thus, our estimate of the entropy will be the weakest aspect of a computer simulation.