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For a system of fermions at room temperature, compute the probability of a single-particle state being occupied if its energy is

(a) 1eVless than μ

(b) 0.01eVless than μ

(c) equal to μ

(d) 0.01eVgreater than μ

(e) 1eVgreater thanμ

Short Answer

Expert verified

According to the Fermi-Dirac distribution, the probability of a state being occupied is given below:

nFD=1e(ε-μ)kT+1

Here, nFDis the Fermi-Dirac distribution, εis the energy, μis the chemical potential, kis the Boltzmann constant, and Tis the absolute temperature.

Formula to energy for the occupied state is given below:

ε-μ=x

Here xis the energy of the state.

Step by step solution

01

(a) Calculate the energy for the occupied state 1 eV less than than μ as follows:

ε-μ=x

Substitute -1eVfor xin the equation ε-μ=x.

ε=μ-1eVε-μ=-1eV

The room temperature in kelvins is,

T=27oC=(27+273)K=300K

Calculate the probability of a state being occupied state 1eVless than μas follows:

nFD=1e(ε-μ)kT+1

Substitute -1eVfor (ε-μ),8.617×10-5eV/Kfor k, and 300Kfor Tin the above equation.

nFD=1e-1eV(8.617×10-3eV/K)(300K)+1=0.9999nFD≈1.0

Therefore, the probability of a state being occupied state1eVless thanμisnFD≈1.0

02

(b) Calculate the energy for the occupied state 0.01 eV less than μ as follows:

ε-μ=x

Substitute -0.01eVfor xin the equation ε-μ=x.

ε=μ-0.01eVε-μ=-0.01eV

The room temperature in kelvins is,

T=27oC=(27+273)K=300K

Calculate the probability of a state being occupied state 0.01eVless than μas follows:

nFD=1e(ε-μ)kT+1

Substitute -0.01eVfor ε-μ, 8.617×10-5eV/Kfor k, and 300Kfor Tin the above equation.

nFD=1e-0.01eV(8.617×10-5eV/K)(300K)+1nFD==0.5955

Therefore, the probability of a state being occupied state0.01eVless thanμisnFD=0.5955

03

(c) Calculate the energy for the occupied state energy is equal to μ as follows:

ε-μ=x

Substitute 0eVfor xin the equation ε-μ=x.

ε=μ-0

The room temperature in kelvins is,

T=27oC=(27+273)K=300K

Calculate the probability of a state being occupied state equal to μas follows:

nFD=1eε-μkT+1

Substitute 0eVfor ε-μ,8.617×10-5eV/Kfor k, and 300Kfor Tin the above equation.

role="math" localid="1647055630164" nFD=1e0eV(8.617×10-5eV/K)(300K)+1nFD=0.5

Therefore, the probability of a state being occupied state equal toμisnFD=0.5

04

(d) Calculate the energy for the occupied state 0.01 eV greater than μ as follows:

ε-μ=x

Substitute 0.01eVfor xin the equation role="math" localid="1647056653513" ε-μ=x

role="math" localid="1647056689711" ε=μ+0.01eVε-μ=0.01eV

The room temperature in kelvins is,

role="math" localid="1647056731594" T=27oC=(27+273)K=300K

Calculate the probability of a state being occupied state 0.01eVless than μas follows:

role="math" nFD=1eε-μkT+1

Substitute 0.01eVfor role="math" localid="1647056852727" ε-μ,8.617×10-5eV/Kfor k, and 300Kfor Tin the above equation.

role="math" localid="1647056921933" nFD=1e0.01eV(8.617×10-5eV/K)(300K)+1nFD=0.4045

Therefore, the probability of a state being occupied state0.01eVgreater thanμisnFD=0.4045

05

(e) Calculate the energy for the occupied state 1 eV greater than μ as follows:

ε-μ=x

Substitute 1eVfor xin the equationε-μ=x

ε=μ+1eVε-μ=1eV

The room temperature in kelvins is,

T=27oC=(27+273)K=300K

Calculate the probability of a state being occupied state role="math" localid="1647056827269" 1eVless than μas follows:

nFD=1eε-μkT+1

Substitute 1eVfor ε-μ,8.617×10-5eV/Kfor k, and 300Kfor Tin the above equation.

role="math" localid="1647057000902" nFD=1e1eV(8.617×10-5eV/K)(300K)+1nFD=1.5852×10-17

Therefore, the probability of a state being occupied state 1eVgreater than μis nFD=1.5852×10-17

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