六方最密堆积

liù fāng zuì mì duī jī

hexagonal close-packed (HCP) (math.)

六

liù

six

方

fāng

square

最

zuì

(before an adjective or verb) to the highest degree; (the) most ...; -est

密

mì

name of an ancient state

堆

duī

to pile up

积

jī

to amass; to accumulate; to store up