[elec_alpha_num]
type: Positive_int
doc: Numbers of electrons alpha ("up")
interface: ezfio, provider

[elec_beta_num]
type: Positive_int
doc: Numbers of electrons beta ("down")
interface: ezfio, provider

[elec_num]
type: Positive_int
doc: Numbers total of electrons (alpha + beta)
default: = electrons.elec_alpha_num + electrons.elec_beta_num
interface: ezfio
